Carbazole derivatives

ABSTRACT

The present invention relates to carbazole derivatives, especially for use in electronic devices. The invention further relates to a process for preparing the compounds of the invention and to electronic devices comprising these.

The present invention relates to carbazole derivatives, especially for use in electronic devices. The invention further relates to a process for preparing the compounds of the invention and to electronic devices comprising these compounds.

Emitting materials used in organic electroluminescent devices (OLEDs) are frequently organometallic complexes which exhibit phosphorescence. For quantum-mechanical reasons, up to four times the energy efficiency and power efficiency is possible using organometallic compounds as phosphorescent emitters. In general terms, there is still a need for improvement in OLEDs, especially also in OLEDs which exhibit phosphorescence, for example with regard to efficiency, operating voltage and lifetime.

The properties of organic electroluminescent devices are not only determined by the emitters used. Also of particular significance here are especially the other materials used, such as host/matrix materials, hole blocker materials, electron transport materials, hole transport materials and electron or exciton blocker materials. Improvements to these materials can lead to distinct improvements to electroluminescent devices.

According to the prior art, examples of matrix materials used for phosphorescent compounds include carbazole derivatives, although there are also known compounds having both carbazole structures and structures derived from benzoxanthene. According to their substitution, these compounds can be used as electron transport materials. For example, KR 2015/0065383 describes corresponding compounds.

However, the benzoxanthene derivatives described include a naphthalene structure with which a carbazole group is formed.

In general terms, in the case of these materials, for example for use as matrix materials, hole conductor materials or electron transport materials, there is still a need for improvement, particularly in relation to the lifetime, but also in relation to the efficiency and operating voltage of the device. Moreover, the compounds should have high colour purity.

The problem addressed by the present invention is therefore that of providing compounds which are suitable for use in an organic electronic device, especially in an organic electroluminescent device, and which lead to good device properties when used in this device, and that of providing the corresponding electronic device.

More particularly, the problem addressed by the present invention is that of providing compounds which lead to a high lifetime, good efficiency and low operating voltage. Particularly the properties of the matrix materials, the hole conductor materials or the electron transport materials too have an essential influence on the lifetime and efficiency of the organic electroluminescent device.

A further problem addressed by the present invention can be considered that of providing compounds suitable for use in a phosphorescent or fluorescent OLED, especially as a matrix material. More particularly, a problem addressed by the present invention is that of providing matrix materials suitable for red-, yellow- and green-phosphorescing OLEDs.

In addition, the compounds, especially when they are used as matrix materials, as hole conductor materials or as electron transport materials in organic electroluminescent devices, should lead to devices having excellent colour purity.

Moreover, the compounds should be processible in a very simple manner, and especially exhibit good solubility and film formation. For example, the compounds should exhibit elevated oxidation stability and an improved glass transition temperature.

A further object can be considered that of providing electronic devices having excellent performance very inexpensively and in constant quality.

Furthermore, it should be possible to use or adapt the electronic devices for many purposes. More particularly, the performance of the electronic devices should be maintained over a broad temperature range.

It has been found that, surprisingly, particular compounds that are described in detail hereinafter solve these problems and eliminate the disadvantage from the prior art. The use of the compounds leads to very good properties of organic electronic devices, especially of organic electroluminescent devices, especially with regard to lifetime, efficiency and operating voltage. The present invention therefore provides electronic devices, especially organic electroluminescent devices, containing such compounds, and the corresponding preferred embodiments.

The present invention therefore provides a compound comprising at least one structure of the following formula (I):

where the symbols used are as follows.

-   X is the same or different at each instance and is N or CR¹,     preferably CR¹, or C if the indolo group is bonded to X; -   W¹ is O, S, C(R¹)₂, P(═O)Ar or Si(R¹)₂, preferably O, S, C(R¹)₂ or     P(═O)Ar, more preferably O, S or C(R¹)₂, most preferably O or S; -   R¹ is the same or different at each instance and is H, D, F, Cl, Br,     I, CN, NO₂, N(Ar¹)₂, N(R²)₂, C(═O)Ar¹, C(═O)R², P(═O)(Ar¹)₂,     P(Ar¹)₂, B(Ar¹)₂, B(OR²)₂, Si(Ar¹)₃, Si(R²)₃, a straight-chain     alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a     branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40     carbon atoms or an alkenyl group having 2 to 40 carbon atoms, each     of which may be substituted by one or more R² radicals, where one or     more nonadjacent CH₂ groups may be replaced by —R²C═CR²—, —C≡—,     Si(R²)₂, Ge(R²)₂, Sn(R²)₂, C═O, C═S, C═Se, C═NR², —C(═O)O—,     —C(═O)NR²—, NR², P(═O)(R²), —O—, —S—, SO or SO₂ and where one or     more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO₂,     or an aromatic or heteroaromatic ring system which has 5 to 40     aromatic ring atoms and may be substituted in each case by one or     more R² radicals, or an aryloxy or heteroaryloxy group which has 5     to 40 aromatic ring atoms and may be substituted by one or more R²     radicals, or an aralkyl or heteroaralkyl group which has 5 to 40     aromatic ring atoms and may be substituted by one or more R²     radicals, or a combination of these systems; at the same time, two     or more preferably adjacent R¹ radicals together may form a mono- or     polycyclic, aliphatic, heteroaliphatic, aromatic or heteroaromatic     ring system; -   Ar is the same or different at each instance and is an aromatic or     heteroaromatic ring system which has 5 to 60 aromatic ring atoms and     may be substituted by one or more preferably nonaromatic R¹     radicals; -   Ar¹ is the same or different at each instance and is an aromatic or     heteroaromatic ring system which has 5 to 30 aromatic ring atoms and     may be substituted by one or more preferably nonaromatic R²     radicals; at the same time, two Ar¹ radicals bonded to the same     silicon atom, nitrogen atom, phosphorus atom or boron atom may also     be joined together via a bridge by a single bond or a bridge     selected from B(R²), C(R²)₂, Si(R²)₂, C═O, C═NR², C═C(R²)₂, O, S,     S═O, SO₂, N(R²), P(R²) and P(═O)R²; -   R² is the same or different at each instance and is H, D, F, Cl, Br,     I, CN, B(OR³)₂, NO₂, C(═O)R³, CR³═C(R³)₂, C(═O)OR³, C(═O)N(R³)₂,     Si(R³)₃, P(R³)₂, B(R³)₂, N(R³)₂, NO₂, P(═O)(R³)₂, OSO₂R³, OR³,     S(═O)R³, S(═O)₂R³, a straight-chain alkyl, alkoxy or thioalkoxy     group having 1 to 40 carbon atoms or a branched or cyclic alkyl,     alkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of     which may be substituted by one or more R³ radicals, where one or     more nonadjacent CH₂ groups may be replaced by —R³C═CR³—, —C≡C—,     Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═NR³, —C(═O)O—, —C(═O)NR³—,     NR³, P(═O)(R³), —O—, —S—, SO or SO₂ and where one or more hydrogen     atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, or an aromatic     or heteroaromatic ring system which has 5 to 40 aromatic ring atoms     and may be substituted in each case by one or more R³ radicals, or     an aryloxy or heteroaryloxy group which has 5 to 40 aromatic ring     atoms and may be substituted by one or more R³ radicals, or a     combination of these systems; at the same time, two or more     preferably adjacent R² substituents together may also form a mono-     or polycyclic, aliphatic, heteroaliphatic, aromatic or     heteroaromatic ring system; -   R³ is the same or different at each instance and is selected from     the group consisting of H, D, F, CN, an aliphatic hydrocarbyl     radical having 1 to 20 carbon atoms, or an aromatic or     heteroaromatic ring system having 5 to 30 aromatic ring atoms in     which one or more hydrogen atoms may be replaced by D, F, Cl, Br, I     or CN and which may be substituted by one or more alkyl groups each     having 1 to 4 carbon atoms; at the same time, two or more preferably     adjacent R³ substituents together may also form a mono- or     polycyclic, aliphatic, heteroaliphatic, aromatic or heteroaromatic     ring system.

The indolo group in formula (I) here binds to two adjacent X atoms. In addition, the indolo group may bind in two alignments, such that the nitrogen atom of the indolo group and the W¹ group are either in cis positions or in trans positions with respect to the central phenyl ring. Adjacent carbon atoms in the context of the present invention are carbon atoms bonded directly to one another. In addition, “adjacent radicals” in the definition of the radicals means that these radicals are bonded to the same carbon atom or to adjacent carbon atoms. These definitions apply correspondingly, inter alia, to the terms “adjacent groups” and “adjacent substituents”.

The wording that two or more radicals together may form a ring, in the context of the present description, shall be understood to mean, inter alia, that the two radicals are joined to one another by a chemical bond with formal elimination of two hydrogen atoms. This is illustrated by the following scheme:

In addition, however, the abovementioned wording shall also be understood to mean that, if one of the two radicals is hydrogen, the second radical binds to the position to which the hydrogen atom was bonded, forming a ring. This shall be illustrated by the following scheme:

A fused aryl group, a fused aromatic ring system or a fused heteroaromatic ring system in the context of the present invention is a group in which two or more aromatic groups are fused, i.e. annelated, to one another along a common edge, such that, for example, two carbon atoms belong to the at least two aromatic or heteroaromatic rings, as, for example, in naphthalene. By contrast, for example, fluorene is not a fused aryl group in the context of the present invention, since the two aromatic groups in fluorene do not have a common edge. Corresponding definitions apply to heteroaryl groups and to fused ring systems which may but need not also contain heteroatoms.

An aryl group in the context of this invention contains 6 to 60 carbon atoms, preferably 6 to 40 carbon atoms, more preferably 6 to 30 carbon atoms; a heteroaryl group in the context of this invention contains 2 to 60 carbon atoms, preferably 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, and at least one heteroatom, with the proviso that the sum total of carbon atoms and heteroatoms is at least 5. The heteroatoms are preferably selected from N, O and/or S. An aryl group or heteroaryl group is understood here to mean either a simple aromatic cycle, i.e. benzene, or a simple heteroaromatic cycle, for example pyridine, pyrimidine, thiophene, etc., or a fused aryl or heteroaryl group, for example naphthalene, anthracene, phenanthrene, quinoline, isoquinoline, etc.

An aromatic ring system in the context of this invention contains 6 to 60 carbon atoms, preferably 6 to 40 carbon atoms, more preferably 6 to 30 carbon atoms, in the ring system. A heteroaromatic ring system in the context of this invention contains 1 to 60 carbon atoms, preferably 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, and at least one heteroatom in the ring system, with the proviso that the sum total of carbon atoms and heteroatoms is at least 5. The heteroatoms are preferably selected from N, O and/or S. An aromatic or heteroaromatic ring system in the context of this invention shall be understood to mean a system which does not necessarily contain only aryl or heteroaryl groups, but in which it is also possible for two or more aryl or heteroaryl groups to be interrupted by a nonaromatic unit (preferably less than 10% of the atoms other than H), for example a carbon, nitrogen or oxygen atom or a carbonyl group. For example, systems such as 9,9′-spirobifluorene, 9,9-diarylfluorene, triarylamine, diary) ethers, stilbene, etc. shall thus also be regarded as aromatic ring systems in the context of this invention, and likewise systems in which two or more aryl groups are interrupted, for example, by a linear or cyclic alkyl group or by a silyl group. In addition, systems in which two or more aryl or heteroaryl groups are bonded directly to one another, for example biphenyl, terphenyl, quaterphenyl or bipyridine, shall likewise be regarded as an aromatic or heteroaromatic ring system.

A cyclic alkyl, alkoxy or thioalkoxy group in the context of this invention is understood to mean a monocyclic, bicyclic or polycyclic group.

In the context of the present invention, a C₁- to C₂₀-alkyl group in which individual hydrogen atoms or CH₂ groups may also be replaced by the abovementioned groups are understood to mean, for example, the methyl, ethyl, n-propyl, i-propyl, cyclopropyl, n-butyl, i-butyl, s-butyl, t-butyl, cyclobutyl, 2-methylbutyl, n-pentyl, s-pentyl, t-pentyl, 2-pentyl, neopentyl, cyclopentyl, n-hexyl, s-hexyl, t-hexyl, 2-hexyl, 3-hexyl, neohexyl, cyclohexyl, 1-methylcyclopentyl, 2-methylpentyl, n-heptyl, 2-heptyl, 3-heptyl, 4-heptyl, cycloheptyl, 1-methylcyclohexyl, n-octyl, 2-ethylhexyl, cyclooctyl, 1-bicyclo[2.2.2]octyl, 2-bicyclo[2.2.2]octyl, 2-(2,6-dimethyl)octyl, 3-(3,7-dimethyl)octyl, adamantyl, trifluoromethyl, pentafluoroethyl, 2,2,2-trifluoroethyl, 1,1-dimethyl-n-hex-1-yl, 1,1-dimethyl-n-hept-1-yl, 1,1-dimethyl-n-oct-1-yl, 1,1-dimethyl-n-dec-1-yl, 1,1-dimethyl-n-dodec-1-yl, 1,1-dimethyl-n-tetradec-1-yl, 1,1-dimethyl-n-hexadec-1-yl, 1,1-dimethyl-n-octadec-1-yl, 1,1-diethyl-n-hex-1-yl, 1,1-diethyl-n-hept-1-yl, 1,1-diethyl-n-oct-1-yl, 1,1-diethyl-n-dec-1-yl, 1,1-diethyl-n-dodec-1-yl, 1,1-diethyl-n-tetradec-1-yl, 1,1-diethyl-n-hexadec-1-yl, 1,1-diethyl-n-octadec-1-yl, 1-(n-propyl)cyclohex-1-yl, 1-(n-butyl)cyclohex-1-yl, 1-(n-hexyl)cyclohex-1-yl, 1-(n-octyl)cyclohex-1-yl and 1-(n-decyl)cyclohex-1-yl radicals. An alkenyl group is understood to mean, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl or cyclooctadienyl. An alkynyl group is understood to mean, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl or octynyl. A C₁- to C₄₀-alkoxy group is understood to mean, for example, methoxy, trifluoromethoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, butoxy, s-butoxy, t-butoxy or 2-methylbutoxy.

An aromatic or heteroaromatic ring system which has 5 to 60, preferably 5-40, aromatic ring atoms, more preferably 5 to 30 aromatic ring atoms, and may also be substituted in each case by the abovementioned radicals and which may be joined to the aromatic or heteroaromatic system via any desired positions is understood to mean, for example, groups derived from benzene, naphthalene, anthracene, benzanthracene, phenanthrene, benzophenanthrene, pyrene, chrysene, perylene, fluoranthene, benzofluoranthene, naphthacene, pentacene, benzopyrene, biphenyl, biphenylene, terphenyl, terphenylene, fluorene, spirobifluorene, dihydrophenanthrene, dihydropyrene, tetrahydropyrene, cis- or trans-indenofluorene, cis- or trans-monobenzoindenofluorene, cis- or trans-dibenzoindenofluorene, truxene, isotruxene, spirotruxene, spiroisotruxene, furan, benzofuran, isobenzofuran, dibenzofuran, thiophene, benzothiophene, isobenzothiophene, dibenzothiophene, pyrrole, indole, isoindole, carbazole, indolocarbazole, indenocarbazole, pyridine, quinoline, isoquinoline, acridine, phenanthridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, phenothiazine, phenoxazine, pyrazole, indazoie, imidazole, benzimidazole, naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazoie, quinoxaiinimidazoie, oxazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, benzothiazole, pyridazine, benzopyridazine, pyrimidine, benzopyrimidine, quinoxaline, 1,5-diazaanthracene, 2,7-diazapyrene, 2,3-diazapyrene, 1,6-diazapyrene, 1,8-diazapyrene, 4,5-diazapyrene, 4,5,9,10-tetraazaperyiene, pyrazine, phenazine, phenoxazine, phenothiazine, fluorubine, naphthyridine, azacarbazole, benzocarboline, phenanthroline, 1,2,3-triazole, 1,2,4-triazole, benzotriazoie, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, tetrazole, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, purine, pteridine, indolizine and benzothiadiazole.

In a preferred configuration, the compounds of the invention may comprise at least one structure of the formula (IIa), (IIb), (IIc), (IId), (IIe) or (IIf)

where the symbols Ar, W¹ and X used have the definition given above, especially for formula (I).

Preferably, the compounds of the invention may comprise at least one structure of the formula (III)

where the symbols R¹, Ar, W¹ and X have the definition given above, especially for formula (I), and m is 0, 1, 2, 3 or 4, preferably 0, 1, 2 or 3,

Preferably, the compounds of the invention may comprise at least one structure of the formula (IIIa), (IIIb), (IIIc), (IIId), (IIIe) or (IIIf)

where the symbols R¹, Ar, W¹ and X have the definition given above, especially for formula (I), and m is 0, 1, 2, 3 or 4, preferably 0, 1, 2 or 3.

In a further preferred embodiment, the compounds of the invention may comprise at least one structure of the formula (IV)

where the symbols R¹, Ar, W¹ and X have the definition given above, especially for formula (I), and o is 0, 1 or 2, preferably 0 or 1.

Preferably, the compounds of the invention may comprise at least one structure of the formula (IVa), (IVb), (IVc), (IVd), (IVe) or (IVf)

where the symbols R¹, Ar, W¹ and X used have the definition set out above, especially for formula (I), and o is 0, 1 or 2, preferably 0 or 1.

In a further preferred configuration, the compounds of the invention may comprise at least one structure of the formula (V)

where the symbols R¹, Ar, W¹ and X have the definition given above, especially for formula (I), and l is 0, 1, 2, 3, 4, 5 or 6, preferably 0, 1, 2, 3 or 4, more preferably 0, 1 or 2.

Preferably, the compounds of the invention may comprise at least one structure of the formula (Va), (Vb), (Vc), (Vd), (Ve) or (Vf)

where the symbols R¹, Ar, W¹ and X used have the definition set out above, especially for formula (I), and l is 0, 1, 2, 3, 4, 5 or 6, preferably 0, 1, 2, 3 or 4, more preferably 0, 1 or 2.

Preference is also given to compounds having structures in which not more than two X groups per ring are N and preferably at least one, more preferably at least two, of the X groups per ring are selected from C—H and C-D.

Preference is further given to compounds having structures of formula (I), (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (III), (IIIa), (IIIb), (IIIc), (IIId), (IIIe), (IIIf), (IV), (IVa), (IVb), (IVc), (IVd), (IVe), (IVf), (V), (Va), (Vb), (Vc), (Vd), (Ve) and/or (Vf) in which not more than four X groups, preferably not more than two X groups and especially not more than one X group is/are N, and more preferably all X groups to which the indolo group is not bonded are CR¹, where preferably not more than four, more preferably not more than three and especially preferably not more than two of the CR¹ groups represented by X are not the CH group.

Preferably, the compounds of the invention may comprise at least one structure of the formula (VI)

where the symbols R¹, Ar and W¹ have the definition given above, especially for formula (I), and l is 0, 1, 2, 3, 4, 5 or 6, preferably 0, 1, 2, 3 or 4, more preferably 0, 1 or 2, m is 0, 1, 2, 3 or 4, preferably 0, 1, 2 or 3, and o is 0, 1 or 2, preferably 0 or 1.

In a further-preferred embodiment, the compounds of the invention may have at least one structure of the formula (VIa), (VIb), (VIc), (VId), (VIe) or (VIf)

where the symbols R¹, Ar and W¹ used have the definition given above, especially for formula (I), 1 is 0, 1, 2, 3, 4, 5 or 6, preferably 0, 1, 2, 3 or 4, more preferably 0, 1 or 2, m is 0, 1, 2, 3 or 4, preferably 0, 1, 2 or 3, and o is 0, 1 or 2, preferably 0 or 1.

In addition, in the structures of the formulae (VI), (VIa), (VIb), (VIc), (VId), (VIe) and/or (VIf), it may be the case that the sum total of the indices l, m and o is not more than 6, preferably not more than 4 and more preferably not more than 2.

In addition, it may be the case that, in the formulae (I), (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (III), (IIIa), (IIIb), (IIIc), (IIId), (IIIe), (IIIf), (IV), (IVa), (IVb), (IVc), (IVd), (IVe), (IVf), (V), (Va), (Vb), (Vc), (Vd), (Ve), (Vf), (VI), (VIa), (VIb), (VIc), (VId), (VIe) and/or (VIf), exactly one R¹ radical that is not H or D is present, and so the other X groups are N, CH or CD, or in other words the sum total of the indices l, m and o is exactly one. Preferably, this R¹ radical is bonded to the carbazole group in these formulae, where the R¹ radical is more preferably bonded to the ring of the carbazole that does not directly have a bond to the W¹ group. This R¹ substituent is preferably in the para position to the nitrogen atom of the carbazole unit.

Preferably, the compounds of the invention may comprise at least one structure of the formula (VII)

where the symbols R¹, Ar and W¹ have the definition given above, especially for formula (I). In this case, R¹ is preferably not H or D.

In a further-preferred embodiment, the compounds of the invention may comprise at least one structure of the formulae (VIIa), (VIIb), (VIIc), (VIId), (IIe) and/or (VIIf)

where the symbols Ar, W¹ and R¹ used have the definition set out above, especially for formula (I). In this case, R¹ is preferably not H or D.

Preferably, the compounds comprising at least one structure of one of the formulae (I) to (VII) or the corresponding preferred embodiments are represented by a structure of one of the formulae (I) to (VII) or the preferred embodiments.

Preferably, the R¹ radical bonded to the carbazole group in the formulae (VII), (VIIa), (VIIb), (VIIc), (VIId), (VIIe) and/or (VIIf) is an aromatic or heteroaromatic ring system which has 5 to 24 aromatic ring atoms, preferably 6 to 13 aromatic ring atoms, and may be substituted in each case by one or more R² radicals, but is preferably unsubstituted. The preferred groups that the R¹ radical bonded to the carbazole group in the formulae (VII), (VIIa), (VIIb), (VIIc), (VIId), (VIIe) and/or (VIIf) may represent especially include phenyl, ortho-, meta- or para-biphenyl, terphenyl, especially branched terphenyl, quaterphenyl, especially branched quaterphenyl, 1- or 2-naphthyl, 1-, 2-, 3- or 4-fluorenyl, 1-, 2-, 3- or 4-spirobifluorenyl, pyridyl, pyrimidinyl, 1-, 2-, 3- or 4-dibenzofuranyl, 1-, 2-, 3- or 4-dibenzothienyl, 1-, 2-, 3- or 4-carbazolyl and indenocarbazolyl, each of which may be substituted by one or more R² radicals, but are preferably unsubstituted. The fluorene or indenocarbazolyl radicals are preferably substituted by two R² radicals on the indeno carbon atom. The carbazole or indenocarbazole radicals are preferably substituted on the nitrogen atom by an R² radical other than H and D, preferably by an aromatic or heteroaromatic R² radical, when they are not bonded via the nitrogen atom.

It may further be the case that the R¹ substituents of the heteroaromatic ring system of the formulae (I), (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (III), (IIIa), (IIIb), (IIIc), (IIId), (IIIe), (IIIf), (IV), (IVa), (IVb), (IVc), (IVd), (IVe), (IVf), (V), (Va), (Vb), (Vc), (Vd), (Ve), (Vf), (VI), (VIa), (VIb), (VIc), (VId), (VIe), (VIf), (VII), (VIIa), (VIIb), (VIIc), (VIId), (VIIe) and/or (VIIf) do not form a fused aromatic or heteroaromatic ring system, preferably any fused ring system, with the ring atoms of the heteroaromatic ring system of the base structure. This includes the formation of a fused ring system with possible R² or R³ substituents which may be bonded to the R¹ radicals.

In a preferred configuration, compounds of the invention can be represented by structures of the formula (I), (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (III), (IIIa), (IIIb), (IIIc), (IIId), (IIIe), (IIIf), (IV), (IVa), (IVb), (IVc), (IVd), (IVe), (IVf), (V), (Va), (Vb), (Vc), (Vd), (Ve), (Vf), (VI), (VIa), (VIb), (VIc), (VId), (VIe), (VIf), (VII), (VIIa), (VIIb), (VIIc), (VIId), (VIIe) and/or (VIIf). Preferably, compounds comprising structures of formula (I), (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (III), (IIIa), (IIIb), (IIIc), (IIId), (IIIe), (IIIf), (IV), (IVa), (IVb), (IVc), (IVd), (IVe), (IVf), (V), (Va), (Vb), (Vc), (Vd), (Ve), (Vf), (VI), (VIa), (VIb), (VIc), (VId), (VIe), (VIf), (VII), (VIIa), (VIIb), (VIIc), (VIId), (VIIe) and/or (VIIf) have a molecular weight of not more than 5000 g/mol, preferably not more than 4000 g/mol, particularly preferably not more than 3000 g/mol, especially preferably not more than 2000 g/mol and most preferably not more than 1200 g/mol.

In addition, it is a feature of preferred compounds of the invention that they are sublimable. These compounds generally have a molar mass of less than about 1200 g/mol.

Preferably, the aromatic or heteroaromatic group of the aromatic or heteroaromatic ring system represented by the symbol Ar or Ar¹ is bonded to the respective atom of the further group directly, i.e. via an atom of the aromatic or heteroaromatic group.

In one embodiment, the Ar group may comprise or constitute a hole transport group. Hole transport groups are known in the technical field, and they preferably include triarylamine or carbazole groups.

It may preferably be the case that the hole transport group comprises a group and preferably is a group selected from the formulae (H-1) to (H-3)

where the dotted bond marks the attachment position to the nitrogen atom and in addition:

-   Ar², Ar³, Ar⁴ are each independently an aryl group having 6 to 40     carbon atoms or a heteroaryl group having 3 to 40 carbon atoms, each     of which may be substituted by one or more R¹ radicals; -   and -   Z is C(R¹)₂, Si(R¹)₂, C═O, N—Ar¹, BR¹, PR¹, PO(R¹), SO, SO₂, Se, O     or S, preferably C(R¹)₂, N—Ar¹, O or S, where the symbols Art and R¹     have the definition given above, especially for formula (I).

Accordingly, the Ar group may comprise a radical of the formulae (H-1) (H-2) and/or (H-3) and may preferably be a radical of the formula (H-1), (H-2) or (H-3).

It may additionally be the case that the Ar group comprises a group and preferably is a group selected from the formulae (H-4) to (H-26)

where Y¹ is O, S, C(R¹)₂ or NAr¹, the dotted bond marks the attachment position to the nitrogen atom, e is 0, 1 or 2, j is 0, 1, 2 or 3, h is the same or different at each instance and is 0, 1, 2, 3 or 4, p is 0 or 1, Ar¹ and R¹ have the definition given above, especially for formula (I), and Ar² has the definition given above, especially for formula (H-1) or (H-2).

The hole transport groups of the formulae (H-1) to (H-26) detailed above also constitute preferred R¹ radicals in the compounds of formula (I) or preferred embodiments of this formula, where in this case the R¹ groups detailed in the formulae (H-1) to (H-26) should be replaced by R² radicals.

It is clear from the above wording that, if the index p=0, the corresponding Ar² group is absent and a bond is formed.

Preferably, the Ar² group may form through-conjugation with the aromatic or heteroaromatic radical or the nitrogen atom to which the Ar² group of the formulae (H-1) to (H-26) may be bonded.

In a further preferred embodiment of the invention, Ar² is an aromatic or heteroaromatic ring system which has 5 to 14 aromatic or heteroaromatic ring atoms, preferably an aromatic ring system which has 6 to 12 carbon atoms, and which may be substituted by one or more R¹ radicals, but is preferably unsubstituted, where R¹ may have the definition given above, especially for formula (I). More preferably, Ar² is an aromatic ring system having 6 to 10 aromatic ring atoms or a heteroaromatic ring system having 6 to 13 heteroaromatic ring atoms, each of which may be substituted by one or more R¹ radicals, but is preferably unsubstituted, where R¹ may have the definition given above, especially for formula (I).

Further preferably, the symbol Ar² shown in formulae (H-1) to (H-26) inter alia is an arylene or heteroarylene radical having 5 to 14 ring atoms, preferably 6 to 13 ring atoms, more preferably 6 to 10 ring atoms, such that an aromatic or heteroaromatic group of an aromatic or heteroaromatic ring system is bonded to the respective atom of the further group directly, i.e. via an atom of the aromatic or heteroaromatic group.

It may additionally be the case that the Ar² group shown in formulae (H-1) to (H-26) comprises an aromatic ring system having not more than two fused aromatic and/or heteroaromatic six-membered rings; preferably, it does not comprise any fused aromatic or heteroaromatic ring system with fused six-membered rings. Accordingly, naphthyl structures are preferred over anthracene structures. In addition, fluorenyl, spirobifluorenyl, dibenzofuranyl and/or dibenzothienyl structures are preferred over naphthyl structures. Particular preference is given to structures having no fusion, for example phenyl, biphenyl, terphenyl and/or quaterphenyl structures.

It may further be the case that the Ar² group shown in formulae (H-1) to (H-26) inter alia has not more than 1 nitrogen atom, preferably not more than 2 heteroatoms, especially preferably not more than one heteroatom and most preferably no heteroatom.

In a further preferred embodiment of the invention, Ar³ and/or Ar⁴ are the same or different at each instance and are an aromatic or heteroaromatic ring system having 6 to 24 aromatic ring atoms, preferably 6 to 18 aromatic ring atoms, and are more preferably an aromatic ring system having 6 to 12 aromatic ring atoms or a heteroaromatic ring system having 6 to 13 aromatic ring atoms, each of which may be substituted by one or more R¹ radicals, but is preferably unsubstituted, where R¹ may have the definition given above, especially in formula (I).

In a further preferred embodiment, the Ar group may comprise, preferably constitute, an electron transport group. Electron transport groups are widely known in the technical field and promote the ability of compounds to transport and/or conduct electrons. Electron-deficient heteroaryl groups in particular are suitable for this purpose. These are defined in that they contain a heteroaromatic six-membered ring having at least one nitrogen atom and/or in that they contain a heteroaromatic five-membered ring having at least two heteroatoms of which at least one heteroatom is nitrogen. It is also possible for further aryl or heteroaryl groups to be fused onto these structures, as for example in quinazoline or benzimidazole.

In this connection, it should be emphasized that compounds of the invention having electron transport groups are particularly preferred as matrix materials and/or electron transport materials, especially also over compounds of the invention that have a hole transport group but no electron transport group.

Furthermore, surprising advantages are exhibited by compounds comprising at least one structure of formula (I) or preferred embodiments thereof in which the Ar group comprises at least one structure selected from the group of the pyridines, pyrimidines, pyrazines, pyridazines, triazines, quinazolines, quinoxalines, quinolines, isoquinolines, imidazoles and/or benzimidazoles, particular preference being given to pyrimidines, triazines and quinazolines.

In a preferred configuration of the present invention, it may be the case that the Ar group is a group that can be represented by the formula (QL)

Q-L¹-   Formula (QL)

in which L¹ represents a bond or an aromatic or heteroaromatic ring system which has 5 to 40, preferably 5 to 30, aromatic ring atoms and may be substituted by one or more R¹ radicals, and Q is an electron transport group, where R¹ has the definition given above, especially for formula (I). In this case, the electron transport group is as defined above.

Preferably, the L¹ group may form through-conjugation with the Q group and the nitrogen atom to which the L¹ group of formula (QL) is bonded. Through-conjugation of the aromatic or heteroaromatic systems is formed as soon as direct bonds are formed between adjacent aromatic or heteroaromatic rings. A further bond between the aforementioned conjugated groups, for example via a sulfur, nitrogen or oxygen atom or a carbonyl group, is not detrimental to conjugation. In the case of a fluorene system, the two aromatic rings are bonded directly, where the sp³-hybridized carbon atom in the 9 position does prevent fusion of these rings, but conjugation is possible, since this sp³-hybridized carbon atom in the 9 position does not necessarily lie between the electron-transporting Q group and the nitrogen atom. In contrast, in the case of a second spirobifluorene structure, through-conjugation can be formed if the bond between the Q group and the aromatic or heteroaromatic radical to which the L¹ group of formula (QL) is bonded is via the same phenyl group in the spirobifluorene structure or via phenyl groups in the spirobifluorene structure that are bonded directly to one another and are in one plane. If the bond between the Q group and the aromatic or heteroaromatic radical to which the L¹ group of formula (QL) is bonded is via different phenyl groups in the second spirobifluorene structure bonded via the sp³-hybridized carbon atom in the 9 position, the conjugation is interrupted.

In a preferred embodiment of the invention, L¹ is a bond or an aromatic or heteroaromatic ring system which has 5 to 14 aromatic or heteroaromatic ring atoms, preferably an aromatic ring system which has 6 to 12 carbon atoms, and which may be substituted by one or more R¹ radicals, but is preferably unsubstituted, where R¹ may have the definition given above, especially for formula (I). More preferably, L¹ is an aromatic ring system having 6 to 10 aromatic ring atoms or a heteroaromatic ring system having 6 to 13 heteroaromatic ring atoms, each of which may be substituted by one or more R¹ radicals, but is preferably unsubstituted, where R¹ may have the definition given above, especially for formula (I).

Further preferably, the symbol L¹ shown in formula (QL) inter alia is the same or different at each instance and is a bond or an arylene or heteroarylene radical having 5 to 24 ring atoms, preferably 6 to 13 ring atoms, more preferably 6 to 10 ring atoms, such that an aromatic or heteroaromatic group of an aromatic or heteroaromatic ring system is bonded to the respective atom of the further group directly, i.e. via an atom of the aromatic or heteroaromatic group.

It may additionally be the case that the L¹ group shown in formula (QL) comprises an aromatic ring system having not more than two fused aromatic and/or heteroaromatic six-membered rings; preferably, it does not comprise any fused aromatic or heteroaromatic ring system. Accordingly, naphthyl structures are preferred over anthracene structures. In addition, fluorenyl, spirobifluorenyl, dibenzofuranyl and/or dibenzothienyl structures are preferred over naphthyl structures.

Particular preference is given to structures having no fusion, for example phenyl, biphenyl, terphenyl and/or quaterphenyl structures.

Examples of suitable aromatic or heteroaromatic ring systems L¹ are selected from the group consisting of ortho-, meta- or para-phenylene, ortho-, meta- or para-biphenylene, terphenylene, especially branched terphenylene, quaterphenylene, especially branched quaterphenylene, fluorenylene, spirobifluorenylene, dibenzofuranylene, dibenzothienylene and carbazolylene, each of which may be substituted by one or more R¹ radicals, but are preferably unsubstituted. When L¹ is carbazolylene, it is preferably substituted on the nitrogen by an R¹ radical other than H and D, preferably by an aromatic or heteroaromatic R¹ radical, when the carbazolylene is not joined via the nitrogen atom.

It may further be the case that the L¹ group shown in formula (QL) inter alia has not more than 1 nitrogen atom, preferably not more than 2 heteroatoms, especially preferably not more than one heteroatom and more preferably no heteroatom.

Preferably; the Q group shown in the formula (QL) inter alia, or the electron transport group, may be selected from structures of the formulae (Q-1), (Q-2), (Q-3), (Q-3), (Q-5), (Q-6), (Q-7), (Q-8), (Q-9) and/or (Q-10)

where the dotted bond marks the attachment position,

Q′ is the same or different at each instance and is CR¹ or N, and

Q″ is NR¹, O or S;

where at least one Q′ is N, and

R¹ is as defined above, especially in formula (I),

In addition, the Q group shown in the formula (QL) inter alia, or the electron transport group, may preferably be selected from a structure of the formulae (Q-11), (Q-12), (Q-13), (Q-14) and/or (Q-15)

where the symbol R¹ has the definition given above for formula (I) inter alia, X is N or CR¹ and the dotted bond marks the attachment position, where X is preferably a nitrogen atom.

In a further embodiment, the Q group shown in the formula (QL) inter alia, or the electron transport group, may be selected from structures of the formulae (Q-16), (Q-17), (Q-18), (Q-19), (Q-20), (Q-21) and/or (Q-22)

in which the symbol R¹ has the definition detailed above for formula (I) inter alia, the dotted bond marks the attachment position and m is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, n is 0, 1, 2 or 3, preferably 0, 1 or 2, and o is 0, 1 or 2, preferably 1 or 2. Preference is given here to the structures of the formulae (Q-16), (Q-17), (Q-18) and (Q-19).

In a further embodiment, the Q group shown in the formula (QL) inter alia, or the electron transport group, may be selected from structures of the formulae (Q-23), (Q-24) and/or (Q-25)

in which the symbol R¹ has the definition set out above for formula (I) inter alia, and the dotted bond marks the attachment position.

In a further embodiment, the Q group shown in the formula (QL) inter alia, or the electron transport group, may be selected from structures of the formulae (Q-26), (Q-27), (Q-28), (Q-29) and/or (Q-30)

where symbols X, Ar¹ and R¹ have the definition given above for formula (I) inter alia and the dotted bond marks the attachment position. Preferably, in the structures of the formulae (Q-26), (Q-27) and (Q-28), exactly one X is a nitrogen atom.

Preferably, the Q group shown in the formula (QL) inter alia, or the electron transport group, may be selected from structures of the formulae (Q-31), (Q-32), (Q-33), (Q-34), (Q-35), (Q-36), (Q-37), (Q-38), (Q-39), (Q-40), (Q-41), (Q-42), (Q-43) and/or (Q-44)

in which the symbols Ar¹ and R¹ have the definition set out above for formula (I) inter alia, the dotted bond marks the attachment position and m is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, n is 0, 1, 2 or 3, preferably 0 or 1, n is 0, 1, 2 or 3, preferably 0, 1 or 2, and l is 1, 2, 3, 4 or 5, preferably 0, 1 or 2.

The electron transport groups of the formulae (Q-1) to (Q-44) detailed above also constitute preferred R¹ radicals in the compounds of formula (I) or preferred embodiments of this formula, where in this case the R¹ groups detailed in the formulae (Q-1) to (Q-44) should be replaced by R² radicals.

It may also be the case that the Ar group comprises a hole transport group and an electron transport group. According to the configuration, preferred groups may be formed from the above-detailed formulae (H-1) to (H-26) or (Q-1) to (Q-44), where, for example, the R¹ groups may be a hole transport or electron transport group, where, for example, the R¹ radicals shown in the formulae (H-1) to (H-26) or (Q-1) to (Q-44) may be replaced by corresponding R² radicals.

In a further preferred embodiment of the invention, Ar¹ is the same or different at each instance and is an aromatic or heteroaromatic ring system, preferably an aryl or heteroaryl radical having 5 to 24 aromatic ring atoms, preferably having 6 to 18 aromatic ring atoms, and is more preferably an aromatic ring system, preferably an aryl radical having 6 to 10 aromatic ring atoms, or a heteroaromatic ring system, preferably a heteroaryl group having 5 to 13 aromatic ring atoms, each of which may be substituted by one or more R² radicals, but is preferably unsubstituted, where R² may have the definition detailed above, especially in formula (I).

Preferably, the symbol Ar¹ is an aryl or heteroaryl radical, such that an aromatic or heteroaromatic group of an aromatic or heteroaromatic ring system is bonded directly, i.e. via an atom of the aromatic or heteroaromatic group, to the respective atom of the further group, for example a carbon or nitrogen atom of the (H-1) to (H-26) or (Q-26) to (Q-44) groups shown above.

Advantageously, Ar¹ in the formulae (H-1) to (H-26) or (Q-26) to (Q-44) is an aromatic ring system which has 6 to 12 aromatic ring atoms and may be substituted by one or more R² radicals, but is preferably unsubstituted, where R² may have the definition detailed above, especially for formula (I).

Preferably, the R¹ or R² radicals in the formulae (H-1) to (H-26) or (Q-1) to (Q-44) do not form a fused ring system with the ring atoms of the aryl group or heteroaryl group Ar¹, Ar², Ar³ and/or Ar⁴ to which the R¹ or R² radicals are bonded. This includes the formation of a fused ring system with possible R² or R³ substituents which may be bonded to the R¹ or R² radicals.

It may further be the case that the Ar, Ar¹, Ar², Ar³ and/or Ar⁴ group is selected from the group consisting of phenyl, ortho-, meta- or para-biphenyl, terphenyl, especially ortho-, meta- or para-terphenyl or branched terphenyl, quaterphenyl, especially ortho-, meta- or para-quaterphenyl or branched quaterphenyl, 1-, 2-, 3- or 4-fluorenyl, 1-, 2-, 3- or 4-spirobifluorenyl, pyridyl, pyrimidinyl, 1-, 2-, 3- or 4-dibenzofuranyl, 1-, 2-, 3- or 4-dibenzothienyl, pyrenyl, triazinyl, imidazolyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, 1-, 2-, 3- or 4-carbazolyl, 1- or 2-naphthyl, anthracenyl, preferably 9-anthracenyl, phenanthrenyl and/or triphenylenyl, each of which may be substituted by one or more R² radicals, but are preferably unsubstituted, particular preference being given to phenyl, spirobifluorene, fluorene, dibenzofuran, dibenzothiophene, anthracene, phenanthrene, triphenylene groups.

When X is CR¹ or when the aromatic and/or heteroaromatic groups are substituted by R¹ substituents, these R¹ substituents are preferably selected from the group consisting of H, D, F, CN, N(Ar¹)₂, C(═O)Ar¹, P(═O)(Ar¹)₂, a straight-chain alkyl or alkoxy group having 1 to 10 carbon atoms or a branched or cyclic alkyl or alkoxy group having 3 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, each of which may be substituted by one or more R² radicals, where one or more nonadjacent CH₂ groups may be replaced by O and where one or more hydrogen atoms may be replaced by D or F, an aromatic or heteroaromatic ring system which has 5 to 24 aromatic ring atoms and may be substituted in each case by one or more R² radicals, but is preferably unsubstituted, or an aralkyl or heteroaralkyl group which has 5 to 25 aromatic ring atoms and may be substituted by one or more R² radicals; at the same time, it is optionally possible for two R¹ substituents preferably bonded to adjacent carbon atoms to form a monocyclic or polycyclic, aliphatic, aromatic or heteroaromatic ring system which may be substituted by one or more R¹ radicals, where the Ar¹ group has the definition given above, especially for formula W.

More preferably, these R¹ substituents are selected from the group consisting of H, D, F, CN, N(Ar¹)₂, a straight-chain alkyl group having 1 to 8 carbon atoms, preferably having 1, 2, 3 or 4 carbon atoms, or a branched or cyclic alkyl group having 3 to 8 carbon atoms, preferably having 3 or 4 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms, preferably having 2, 3 or 4 carbon atoms, each of which may be substituted by one or more R² radicals, but is preferably unsubstituted, or an aromatic or heteroaromatic ring system which has 5 to 24 aromatic ring atoms, preferably 6 to 18 aromatic ring atoms, more preferably 6 to 13 aromatic ring atoms, and may be substituted in each case by one or more nonaromatic R¹ radicals, but is preferably unsubstituted; at the same time, two R¹ substituents preferably bonded to adjacent carbon atoms may optionally form a monocyclic or polycyclic aliphatic ring system which may be substituted by one or more R² radicals, but is preferably unsubstituted, where Ar¹ may have the definition set out above.

Most preferably, the R¹ substituents are selected from the group consisting of H and an aromatic or heteroaromatic ring system which has 6 to 18 aromatic ring atoms, preferably 6 to 13 aromatic ring atoms, and may be substituted in each case by one or more nonaromatic R² radicals, but is preferably unsubstituted. Examples of suitable R¹ substituents are selected from the group consisting of phenyl, ortho-, meta- or para-biphenyl, terphenyl, especially branched terphenyl, quaterphenyl, especially branched quaterphenyl, 1-, 2-, 3- or 4-fluorenyl, 1-, 2-, 3- or 4-spirobifluorenyl, pyridyl, pyrimidinyl, 1-, 2-, 3- or 4-dibenzofuranyl, 1-, 2-, 3- or 4-dibenzothienyl and 1-, 2-, 3- or 4-carbazolyl, each of which may be substituted by one or more R² radicals, but are preferably unsubstituted.

It may further be the case that, in a structure of formula (I), (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (III), (IIIa), (IIIb), (IIIc), (IIId), (IIIe), (IIIf), (IV), (IVa), (IVb), (IVc), (IVd), (IVe), (IVf), (V), (Va), (Vb), (Vc), (Vd), (Ve), (Vf), (VI), (VIa), (VIb), (VIc), (VId), (VIe), (VIf), (VII), (VIIa), (VIIb), (VIIc), (VIId), (VIIe) and/or (VIIf), at least one R¹ or AO radical is a group selected from the formulae (R¹-1) to (R¹-92), or, in a structure of formula (H-1) to (H-26), (Q-1) to (Q-44), at least one AO or R¹ radical is a group selected from the formulae (R¹-1) to (R¹-92)

where the symbols used are as follows:

Y is O, S or NR², preferably O or S;

k at each instance is independently 0 or 1;

i at each instance is independently 0, 1 or 2;

at each instance is independently 0, 1, 2 or 3;

h at each instance is independently 0, 1, 2, 3 or 4;

g at each instance is independently 0, 1, 2, 3, 4 or 5;

R² may have the definition given above, especially for formula (I);

the dotted bond marks the attachment position.

Preference is given here to the groups of the formulae R¹-1 to R¹-56, particular preference to the R¹-1, R¹-3, R¹-5, R¹-6, R¹-15, R¹-29, R¹-30, R¹-31, R¹-32, R¹-33, R¹-38, R¹-39, R¹-40, R¹-41, R¹-42, R¹-43, R¹-44 and/or R¹-45 groups.

It may preferably be the case that the sum total of the indices k, i, j, h and g in the structures of the formula (R¹-1) to (R¹-92) in each case is not more than 3, preferably not more than 2 and more preferably not more than 1.

Preferably, the R² radicals in the formulae (R¹-1) to (R¹-92) do not form a fused aromatic or heteroaromatic ring system, and preferably do not form any fused ring system, with the ring atoms of the aryl group or heteroaryl group to which the R² radicals are bonded. This includes the formation of a fused ring system with possible R³ substituents which may be bonded to the R² radicals.

The above-detailed radicals of the formulae (R¹-1) to (R′-92) are preferred Ar radicals of formula (I) or Ar³, Ar⁴ radicals of formulae (H-1) to (H-3) or preferred embodiments of these formulae, where, in this case, the R² groups shown in the formulae (R¹-1) to (R¹-92) are to be replaced by R¹ radicals. The preferences detailed above with regard to the formulae (R¹-1) to (R¹-92) are correspondingly applicable.

Preference is given to compounds comprising at least one structure of the formulae (H-1) to (H-26) in which the Are group is a group selected from the formulae (L¹-1) to (L¹-108) and/or to compounds comprising structures of the formula (QL) in which the L¹ group is a bond or is a group selected from the formulae (L¹-1) to (L¹-108)

where the dotted bonds in each case mark the attachment positions, the index k is 0 or 1, the index l is 0, 1 or 2, the index j at each instance is independently 0, 1, 2 or 3; the index h at each instance is independently 0, 1, 2, 3 or 4, the index g is 0, 1, 2, 3, 4 or 5; the symbol Y is O, S or NR¹, preferably O or S; and the symbol R¹ has the definition given above, especially for formula (I).

It may preferably be the case that the sum total of the indices k, l, g, h and j in the structures of the formula (L¹-1) to (L¹-108) is at most 3 in each case, preferably at most 2 and more preferably at most 1.

Preferred compounds of the invention having a group of the formulae (H-1) to (H-26) comprise an Are group selected from one of the formulae (L¹-1) to (L¹-78) and/or (L¹-92) to (L¹-108), preferably of the formula (L¹-1) to (L¹-54) and/or (L¹-92) to (L¹-108), especially preferably of the formula (L¹-1) to (L¹-29) and/or (L¹-92) to (L¹-103). Advantageously, the sum total of the indices k, l, g, h and j in the structures of the formulae (L¹-1) to (L¹-78) and/or (L¹-92) to (L¹-108), preferably of the formula (L¹-1) to (L¹-54) and/or (L¹-92) to (L¹-108), especially preferably of the formula (L¹-1) to (L¹-29) and/or (L¹-92) to (L¹-103), may in each case be not more than 3, preferably not more than 2 and more preferably not more than 1.

Preferred compounds of the invention having a group of the formula (QL) comprise an L¹ group which represents a bond or which is selected from one of the formulae (L¹-1) to (L¹-78) and/or (L¹-92) to (L¹-108), preferably of the formula (L¹-1) to (L¹-54) and/or (L¹-92) to (L¹-108), especially preferably of the formula (L¹-1) to (L¹-29) and/or (L¹-92) to (L¹-103). Advantageously, the sum total of the indices k, l, g, h and j in the structures of the formulae (L¹-1) to (L¹-78) and/or (L¹-92) to (L¹-108), preferably of the formula (L¹-1) to (L¹-54) and/or (L¹-92) to (L¹-108), especially preferably of the formula (L¹-1) to (L¹-29) and/or (L¹-92) to (L¹-103), may in each case be not more than 3, preferably not more than 2 and more preferably not more than 1.

Preferably, the R² radicals in the formulae (L¹-1) to (L¹-108) do not form a fused aromatic or heteroaromatic ring system, and preferably do not form any fused ring system, with the ring atoms of the aryl group or heteroaryl group to which the R² radicals are bonded. This includes the formation of a fused ring system with possible R³ substituents which may be bonded to the R² radicals.

When the compound of the invention is substituted by aromatic or heteroaromatic R¹ or R² groups, it is preferable when these do not have any aryl or heteroaryl groups having more than two aromatic six-membered rings fused directly to one another. More preferably, the substituents do not have any aryl or heteroaryl groups having six-membered rings fused directly to one another at all. The reason for this preference is the low triplet energy of such structures. Fused aryl groups which have more than two aromatic six-membered rings fused directly to one another but are nevertheless also suitable in accordance with the invention are phenanthrene and triphenylene, since these also have a high triplet level.

In a further preferred embodiment of the invention, R², for example in a structure of formula (I) and preferred embodiments of this structure or the structures where reference is made to these formulae, is the same or different at each instance and is selected from the group consisting of H, D, an aliphatic hydrocarbyl radical having 1 to 10 carbon atoms, preferably having 1, 2, 3 or 4 carbon atoms, or an aromatic or heteroaromatic ring system which has 5 to 30 aromatic ring atoms, preferably 5 to 24 aromatic ring atoms, more preferably 5 to 13 aromatic ring atoms, and may be substituted by one or more alkyl groups each having 1 to 4 carbon atoms, but is preferably unsubstituted.

Preferably, the R² radicals do not form a fused aromatic or heteroaromatic ring system, and preferably do not form any fused ring system, with the ring atoms of the aryl group or heteroaryl group to which the R² radicals are bonded. This includes the formation of a fused ring system with possible R³ substituents which may be bonded to the R² radicals.

In a further preferred embodiment of the invention, R³, for example in a structure of formula (I) and preferred embodiments of this structure or the structures where reference is made to these formulae, is the same or different at each instance and is selected from the group consisting of H, D, F, CN, an aliphatic hydrocarbyl radical having 1 to 10 carbon atoms, preferably having 1, 2, 3 or 4 carbon atoms, or an aromatic or heteroaromatic ring system which has 5 to 30 aromatic ring atoms, preferably 5 to 24 aromatic ring atoms, more preferably 5 to 13 aromatic ring atoms, and may be substituted by one or more alkyl groups each having 1 to 4 carbon atoms, but is preferably unsubstituted.

Examples of suitable compounds of the invention are the structures of the following formulae 1 to 153 shown below.

Preferred embodiments of compounds of the invention are recited specifically in the examples, these compounds being usable alone or in combination with further compounds for all purposes of the invention.

Provided that the conditions specified in claim 1 are complied with, the abovementioned preferred embodiments can be combined with one another as desired. In a particularly preferred embodiment of the invention, the abovementioned preferred embodiments apply simultaneously.

The compounds of the invention are preparable in principle by various processes. However, the processes described hereinafter have been found to be particularly suitable.

Therefore, the present invention further provides a process for preparing the compounds comprising structures of formula (I) in which, in a coupling reaction, a compound comprising at least one nitrogen-containing heterocyclic group is joined to a compound comprising at least one aromatic or heteroaromatic group.

Suitable compounds having a carbazole group are in many cases commercially available, and the starting compounds detailed in the examples are obtainable by known processes, and so reference is made thereto.

These compounds can be reacted with further aryl compounds by known coupling reactions, the necessary conditions for this purpose being known to the person skilled in the art, and detailed specifications in the examples give support to the person skilled in the art in conducting these reactions.

Particularly suitable and preferred coupling reactions which all lead to C—C bond formation and/or C—N bond formation are those according to BUCHWALD, SUZUKI, YAMAMOTO, STILLE, HECK, NEGISHI, SONOGASHIRA and HIYAMA. These reactions are widely known, and the examples will provide the person skilled in the art with further pointers.

In all the synthesis schemes which follow, the compounds are shown with a small number of substituents to simplify the structures. This does not rule out the presence of any desired further substituents in the processes.

An illustrative implementation is given by the schemes which follow, without any intention that these should impose a restriction. The component steps of the individual schemes may be combined with one another as desired.

The definition of the symbols used in Schemes 1 and 2 corresponds essentially to those defined for formula (I), dispensing with numbering for reasons of clarity.

The processes shown for synthesis of the compounds of the invention should be understood by way of example. The person skilled in the art will be able to develop alternative synthesis routes within the scope of his common knowledge in the art.

The principles of the preparation processes detailed above are known in principle from the literature for similar compounds and can be adapted easily by the person skilled in the art to the preparation of the compounds of the invention. Further information can be found in the examples.

It is possible by these processes, if necessary followed by purification, for example recrystallization or sublimation, to obtain the compounds of the invention comprising structures of formula (I) in high purity, preferably more than 99% (determined by means of ¹H NMR and/or HPLC).

The compounds of the invention may also have suitable substituents, for example relatively long alkyl groups (about 4 to 20 carbon atoms), especially branched alkyl groups, or optionally substituted aryl groups, for example xylyl, mesityl or branched terphenyl or quaterphenyl groups, which bring about solubility in standard organic solvents, such that the compounds are soluble at room temperature in toluene or xylene, for example, in sufficient concentration to be able to process the compounds from solution. These soluble compounds are of particularly good suitability for processing from solution, for example by printing methods. In addition, it should be emphasized that the compounds of the invention comprising at least one structure of the formula (I) already have enhanced solubility in these solvents.

The compounds of the invention may also be mixed with a polymer. It is likewise possible to incorporate these compounds covalently into a polymer. This is especially possible with compounds substituted by reactive leaving groups such as bromine, iodine, chlorine, boronic acid or boronic ester, or by reactive polymerizable groups such as olefins or oxetanes. These may find use as monomers for production of corresponding oligomers, dendrimers or polymers. The oligomerization or polymerization is preferably effected via the halogen functionality or the boronic acid functionality or via the polymerizable group. It is additionally possible to crosslink the polymers via groups of this kind. The compounds and polymers of the invention may be used in the form of a crosslinked or uncrosslinked layer.

The invention therefore further provides oligomers, polymers or dendrimers containing one or more of the above-detailed structures of the formula (I) or compounds of the invention, wherein there are one or more bonds of the compounds of the invention or of the structures of the formula (I) to the polymer, oligomer or dendrimer. According to the linkage of the structures of the formula (I) or of the compounds, these therefore form a side chain of the oligomer or polymer or are bonded within the main chain. The polymers, oligomers or dendrimers may be conjugated, partly conjugated or nonconjugated. The oligomers or polymers may be linear, branched or dendritic. For the repeat units of the compounds of the invention in oligomers, dendrimers and polymers, the same preferences apply as described above.

For preparation of the oligomers or polymers, the monomers of the invention are homopolymerized or copolymerized with further monomers. Preference is given to copolymers wherein the units of formula (I) or the preferred embodiments recited above and hereinafter are present to an extent of 0.01 to 99.9 mol %, preferably 5 to 90 mol %, more preferably 20 to 80 mol %. Suitable and preferred comonomers which form the polymer base skeleton are chosen from fluorenes (for example according to EP 842208 or WO 2000/022026), spirobifluorenes (for example according to EP 707020, EP 894107 or WO 2006/061181), paraphenylenes (for example according to WO 92/18552), carbazoles (for example according to WO 2004/070772 or WO 2004/113468), thiophenes (for example according to EP 1028136), dihydrophenanthrenes (for example according to WO 2005/014689), cis- and trans-indenofluorenes (for example according to WO 2004/041901 or WO 2004/113412), ketones (for example according to WO 2005/040302), phenanthrenes (for example according to WO 2005/104264 or WO 2007/017066) or else a plurality of these units. The polymers, oligomers and dendrimers may contain still further units, for example hole transport units, especially those based on triarylamines, and/or electron transport units.

Additionally of particular interest are compounds of the invention which feature a high glass transition temperature. In this connection, preference is given especially to compounds of the invention comprising structures of the general formula (I) or the preferred embodiments recited above and hereinafter which have a glass transition temperature of at least 70° C., more preferably of at least 110° C., even more preferably of at least 125° C. and especially preferably of at least 150° C., determined in accordance with DIN 51005 (2005-08 version).

For the processing of the compounds of the invention from a liquid phase, for example by spin-coating or by printing methods, formulations of the compounds of the invention are required. These formulations may, for example, be solutions, dispersions or emulsions. For this purpose, it may be preferable to use mixtures of two or more solvents. Suitable and preferred solvents are, for example, toluene, anisole, 0-, m- or p-xylene, methyl benzoate, mesitylene, tetralin, veratrole, THE, methyl-THF, THP, chlorobenzene, dioxane, phenoxytoluene, especially 3-phenoxytoluene, (−)-fenchone, 1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, 1-methylnaphthalene, 2-methylbenzothiazole, 2-phenoxyethanol, 2-pyrrolidinone, 3-methylanisole, 4-methylanisole, 3,4-dimethylanisole, 3,5-dimethylanisole, acetophenone, α-terpineol, benzothiazole, butyl benzoate, cumene, cyclohexanol, cyclohexanone, cyclohexylbenzene, decalin, dodecylbenzene, ethyl benzoate, indane, NMP, p-cymene, phenetole, 1,4-diisopropylbenzene, dibenzyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, diethylene glycol monobutyl ether, tripropylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 2-isopropyl naphthalene, pentylbenzene, hexylbenzene, heptylbenzene, octylbenzene, 1,1-bis(3,4-dimethylphenyl)ethane, hexamethylindane, 2-methylbiphenyl, 3-methylbiphenyl, 1-methylnaphthalene, 1-ethylnaphthalene, ethyl octanoate, diethyl sebacate, octyl octanoate, heptylbenzene, menthyl isovalerate, cyclohexyl hexanoate or mixtures of these solvents.

The present invention therefore further provides a formulation comprising a compound of the invention and at least one further compound. The further compound may, for example, be a solvent, especially one of the abovementioned solvents or a mixture of these solvents. The further compound may alternatively be at least one further organic or inorganic compound which is likewise used in the electronic device, for example an emitting compound, for example a fluorescent dopant, a phosphorescent dopant or a compound that exhibits TADF (thermally activated delayed fluorescence), especially a phosphorescent dopant, and/or a further matrix material. This further compound may also be polymeric.

The present invention therefore still further provides a composition comprising a compound of the invention and at least one further organically functional material. Functional materials are generally the organic or inorganic materials introduced between the anode and cathode. Preferably, the organically functional material is selected from the group consisting of fluorescent emitters, phosphorescent emitters, emitters that exhibit TADF (thermally activated delayed fluorescence), host materials, electron transport materials, electron injection materials, hole conductor materials, hole injection materials, electron blocker materials, hole blocker materials, wide band gap materials and n-dopants.

The present invention therefore also relates to a composition comprising at least one compound comprising structures of formula (I) or the preferred embodiments recited above and hereinafter and at least one further matrix material. According to a particular aspect of the present invention, the further matrix material has hole-transporting properties.

The present invention further provides a composition comprising at least one compound comprising at least one structure of formula (I) or the preferred embodiments recited above and hereinafter and at least one wide band gap material, a wide band gap material being understood to mean a material in the sense of the disclosure of U.S. Pat. No. 7,294,849. These systems exhibit exceptional advantageous performance data in electroluminescent devices.

Preferably, the additional compound may have a band gap of 2.5 eV or more, preferably 3.0 eV or more, very preferably of 3.5 eV or more. One way of calculating the band gap is via the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

Molecular orbitals, especially also the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the energy levels thereof and the energy of the lowest triplet state T₁ and that of the lowest excited singlet state Si of the materials are determined via quantum-chemical calculations. For calculation of organic substances without metals, an optimization of geometry is first conducted by the “Ground State/Semi-empirical/Default Spin/AM1/Charge 0/Spin Singlet” method. Subsequently, an energy calculation is effected on the basis of the optimized geometry. This is done using the “TD-SCF/DFT/Default Spin/B3PW91” method with the “6-31G(d)” basis set (charge 0, spin singlet). For metal-containing compounds, the geometry is optimized via the “Ground State/Hartree-Fock/Default Spin/LanL2 MB/Charge 0/Spin Singlet” method. The energy calculation is effected analogously to the above-described method for the organic substances, except that the “LanL2DZ” basis set is used for the metal atom and the “6-31G(d)” basis set for the ligands. The HOMO energy level HEh or LUMO energy level LEh is obtained from the energy calculation in Hartree units. This is used to determine the HOMO and LUMO energy levels in electron volts, calibrated by cyclic voltammetry measurements, as follows:

HOMO(eV)=((HEh*27.212)−0.9899)/1.1206

LUMO(eV)=((LEh*27.212)−2.0041)/1.385

These values are to be regarded as HOMO and LUMO energy levels of the materials in the context of this application.

The lowest triplet state Ti is defined as the energy of the triplet state having the lowest energy, which is apparent from the quantum-chemical calculation described.

The lowest excited singlet state Si is defined as the energy of the excited singlet state having the lowest energy, which is apparent from the quantum-chemical calculation described.

The method described herein is independent of the software package used and always gives the same results. Examples of frequently utilized programs for this purpose are “Gaussian09 W” (Gaussian Inc.) and Q-Chem 4.1 (Q-Chem, Inc.).

The present invention also relates to a composition comprising at least one compound comprising structures of formula (I) or the preferred embodiments recited above and hereinafter and at least one phosphorescent emitter, the term “phosphorescent emitters” also being understood to mean phosphorescent dopants.

A dopant in a system comprising a matrix material and a dopant is understood to mean that component having the smaller proportion in the mixture. Correspondingly, a matrix material in a system comprising a matrix material and a dopant is understood to mean that component having the greater proportion in the mixture.

Preferred phosphorescent dopants for use in matrix systems, preferably mixed matrix systems, are the preferred phosphorescent dopants specified hereinafter.

The term “phosphorescent dopants” typically encompasses compounds where the emission of light is effected through a spin-forbidden transition, for example a transition from an excited triplet state or a state having a higher spin quantum number, for example a quintet state.

Suitable phosphorescent compounds (=triplet emitters) are especially compounds which, when suitably excited, emit light, preferably in the visible region, and also contain at least one atom of atomic number greater than 20, preferably greater than 38 and less than 84, more preferably greater than 56 and less than 80, especially a metal having this atomic number. Preferred phosphorescence emitters used are compounds containing copper, molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold or europium, especially compounds containing iridium or platinum. In the context of the present invention, all luminescent compounds containing the abovementioned metals are regarded as phosphorescent compounds.

Examples of the above-described emitters can be found in applications WO 00/70655, WO 2001/41512, WO 2002/02714, WO 2002/15645, EP 1191613, EP 1191612, EP 1191614, WO 05/033244, WO 05/019373, US 2005/0258742, WO 2009/146770, WO 2010/015307, WO 2010/031485, WO 2010/054731, WO 2010/054728, WO 2010/086089, WO 2010/099852, WO 2010/102709, WO 2011/032626, WO 2011/066898, WO 2011/157339, WO 2012/007086, WO 2014/008982, WO 2014/023377, WO 2014/094961, WO 2014/094960, WO 2015/036074, WO 2015/104045, WO 2015/117718, WO 2016/015815, WO 2016/124304, WO 2017/032439 and the as yet unpublished applications EP16179378.1 and EP16186313.9. In general, all phosphorescent complexes as used for phosphorescent OLEDs according to the prior art and as known to those skilled in the art in the field of organic electroluminescence are suitable, and the person skilled in the art will be able to use further phosphorescent complexes without exercising inventive skill.

Explicit examples of phosphorescent dopants are adduced in the following table:

The above-described compound comprising structures of the formula (I) or the above-detailed preferred embodiments can preferably be used as active component in an electronic device. An electronic device is understood to mean any device comprising anode, cathode and at least one layer between anode and cathode, said layer comprising at least one organic or organometallic compound. The electronic device of the invention thus comprises anode, cathode and at least one intervening layer containing at least one compound comprising structures of the formula (I). Preferred electronic devices here are selected from the group consisting of organic electroluminescent devices (OLEDs, PLEDs), organic integrated circuits (O-ICs), organic field-effect transistors (O-FETs), organic thin-film transistors (O-TFTs), organic light-emitting transistors (O-LETs), organic solar cells (O-SCs), organic optical detectors, organic photoreceptors, organic field-quench devices (O-FQDs), organic electrical sensors, light-emitting electrochemical cells (LECs), organic laser diodes (O-lasers) and organic plasmon emitting devices (D. M. Koller et al., Nature Photonics 2008, 1-4), preferably organic electroluminescent devices (OLEDs, PLEDs), especially phosphorescent OLEDs, containing at least one compound comprising structures of the formula (I) in at least one layer. Particular preference is given to organic electroluminescent devices. Active components are generally the organic or inorganic materials introduced between the anode and cathode, for example charge injection, charge transport or charge blocker materials, but especially emission materials and matrix materials.

A preferred embodiment of the invention is organic electroluminescent devices. The organic electroluminescent device comprises cathode, anode and at least one emitting layer. Apart from these layers, it may comprise still further layers, for example in each case one or more hole injection layers, hole transport layers, hole blocker layers, electron transport layers, electron injection layers, exciton blocker layers, electron blocker layers, charge generation layers and/or organic or inorganic p/n junctions. At the same time, it is possible that one or more hole transport layers are p-doped, for example with metal oxides such as MoO₃ or WO₃ or with (per)fluorinated electron-deficient aromatic systems, and/or that one or more electron transport layers are n-doped. It is likewise possible for interlayers to be introduced between two emitting layers, these having, for example, an exciton-blocking function and/or controlling the charge balance in the electroluminescent device. However, it should be pointed out that not necessarily every one of these layers need be present.

In this case, it is possible for the organic electroluminescent device to contain an emitting layer, or for it to contain a plurality of emitting layers. If a plurality of emission layers are present, these preferably have several emission maxima between 380 nm and 750 nm overall, such that the overall result is white emission; in other words, various emitting compounds which may fluoresce or phosphoresce are used in the emitting layers. Especially preferred are three-layer systems where the three layers exhibit blue, green and orange or red emission (for the basic construction see, for example, WO 2005/011013), or systems having more than three emitting layers. Preference is further given to tandem OLEDs as well. The system may also be a hybrid system wherein one or more layers fluoresce and one or more other layers phosphoresce.

In a preferred embodiment of the invention, the organic electroluminescent device contains the compound of the invention comprising structures of formula (I) or the above-detailed preferred embodiments as matrix material, preferably as electron-conducting matrix material, in one or more emitting layers, preferably in combination with a further matrix material, preferably a hole-conducting matrix material. In a further preferred embodiment of the invention, the further matrix material is an electron-transporting compound. In yet a further preferred embodiment, the further matrix material is a compound having a large band gap which is not involved to a significant degree, if at all, in the hole and electron transport in the layer. An emitting layer comprises at least one emitting compound.

Suitable matrix materials which can be used in combination with the compounds of formula (I) or according to the preferred embodiments are aromatic ketones, aromatic phosphine oxides or aromatic sulfoxides or sulfones, for example according to WO 2004/013080, WO 2004/093207, WO 2006/005627 or WO 2010/006680, triarylamines, especially monoamines, for example according to WO 2014/015935, carbazole derivatives, e.g. CBP (N,N-biscarbazolylbiphenyl) or the carbazole derivatives disclosed in WO 2005/039246, US 2005/0069729, JP 2004/288381, EP 1205527 or WO 2008/086851, indolocarbazole derivatives, for example according to WO 2007/063754 or WO 2008/056746, indenocarbazole derivatives, for example according to WO 2010/136109 and WO 2011/000455, azacarbazole derivatives, for example according to EP 1617710, EP 1617711, EP 1731584, JP 2005/347160, bipolar matrix materials, for example according to WO 2007/137725, silanes, for example according to WO 2005/111172, azaboroles or boronic esters, for example according to WO 2006/117052, triazine derivatives, for example according to WO 2010/015306, WO 2007/063754 or WO 2008/056746, zinc complexes, for example according to EP 652273 or WO 2009/062578, diazasilole or tetraazasilole derivatives, for example according to WO 2010/054729, diazaphosphole derivatives, for example according to WO 2010/054730, bridged carbazole derivatives, for example according to US 2009/0136779, WO 2010/050778, WO 2011/042107, WO 2011/088877 or WO 2012/143080, triphenylene derivatives, for example according to WO 2012/048781, lactams, for example according to WO 2011/116865, WO 2011/137951 or WO 2013/064206, 4-spirocarbazole derivatives, for example according to WO 2014/094963 or WO 2015/192939, or dibenzofuran derivatives, for example according to WO 2015/169412, WO 2016/015810, WO 2016/023608, WO 2017/148564 or WO 2017/148565. It is likewise possible for a further phosphorescent emitter which emits at a shorter wavelength than the actual emitter to be present as co-host in the mixture.

Preferred co-host materials are triarylamine derivatives, especially monoamines, indenocarbazole derivatives, 4-spirocarbazole derivatives, lactams and carbazole derivatives.

Preferred triarylamine derivatives which are used as co-host materials together with the compounds of the invention are selected from the compounds of the following formula (TA-1):

where Ar⁵ is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 6 to 40 carbon atoms and may be substituted in each case by one or more R² radicals, where two or more adjacent R² substituents may optionally form a mono- or polycyclic, aliphatic ring system which may be substituted by one or more R³ radicals, where the symbol R² is as defined above, especially for formula (I). Preferably, Ar⁵ is the same or different at each instance and is an aryl or heteroaryl group which has 5 to 24 and preferably 5 to 12 aromatic ring atoms, and which may be substituted in each case by one or more R² radicals, but is preferably unsubstituted.

Examples of suitable Ar⁵ groups are selected from the group consisting of phenyl, ortho-, meta- or para-biphenyl, terphenyl, especially branched terphenyl, quaterphenyl, especially branched quaterphenyl, 1-, 2-, 3- or 4-fluorenyl, 1-, 2-, 3- or 4-spirobifluorenyl, pyridyl, pyrimidinyl, 1-, 2-, 3- or 4-dibenzofuranyl, 1-, 2-, 3- or 4-dibenzothienyl and 1-, 2-, 3- or 4-carbazolyl, each of which may be substituted by one or more R² radicals, but are preferably unsubstituted.

Preferably, the Ar⁵ groups are the same or different at each instance and are selected from the abovementioned R¹-1 to R¹-92 groups, more preferably R¹-1 to R¹-54.

In a preferred embodiment of the compounds of the formula (TA-1), at least one Ar⁵ group is selected from a biphenyl group, which may be an ortho-, meta- or para-biphenyl group. In a further preferred embodiment of the compounds of the formula (TA-1), at least one Ar⁵ group is selected from a fluorene group or spirobifluorene group, where these groups may each be bonded to the nitrogen atom in the 1, 2, 3 or 4 position. In yet a further preferred embodiment of the compounds of the formula (TA-1), at least one Ar⁵ group is selected from a phenylene or biphenyl group, where the group is an ortho-, meta- or para-bonded group, substituted by a dibenzofuran group, a dibenzothiophene group or a carbazole group, especially a dibenzofuran group, where the dibenzofuran or dibenzothiophene group is bonded to the phenylene or biphenyl group via the 1, 2, 3 or 4 position and where the carbazole group is bonded to the phenylene or biphenyl group via the 1, 2, 3 or 4 position or via the nitrogen atom.

In a particularly preferred embodiment of the compounds of the formula (TA-1), one Ar⁵ group is selected from a fluorene or spirobifluorene group, especially a 4-fluorene or 4-spirobifluorene group, and one Ar⁵ group is selected from a biphenyl group, especially a para-biphenyl group, or a fluorene group, especially a 2-fluorene group, and the third Ar⁵ group is selected from a para-phenylene group or a para-biphenyl group, substituted by a dibenzofuran group, especially a 4-dibenzofuran group, or a carbazole group, especially an N-carbazole group or a 3-carbazole group.

Preferred indenocarbazole derivatives which are used as co-host materials together with the compounds of the invention are selected from the compounds of the following formula (TA-2):

where Ar⁵ and R¹ have the definitions listed above, especially for formulae (I) and/or (TA-1). Preferred embodiments of the Ar⁵ group are the above-listed structures R¹-1 to R¹-92, more preferably R¹-1 to R¹-54.

A preferred embodiment of the compounds of the formula (TA-2) is the compounds of the following formula (TA-2a):

where Ar⁵ and R¹ have the definitions listed above, especially for formulae (I) and/or (TA-1). The two R¹ groups bonded to the indeno carbon atom here are preferably the same or different and are an alkyl group having 1 to 4 carbon atoms, especially methyl groups, or an aromatic ring system having 6 to 12 carbon atoms, especially phenyl groups. More preferably, the two R¹ groups bonded to the indeno carbon atom are methyl groups. Further preferably, the R¹ substituent bonded to the indenocarbazole base skeleton in formula (TA-2a) is H or a carbazole group which may be bonded to the indenocarbazole base skeleton via the 1, 2, 3 or 4 position or via the nitrogen atom, especially via the 3 position.

Preferred 4-spirocarbazole derivatives which are used as co-host materials together with the compounds of the invention are selected from the compounds of the following formula (TA-3):

where Ar⁵ and R¹ have the definitions listed above, especially for formulae (I) and/or (TA-1). Preferred embodiments of the Ar⁵ group are the above-listed structures R¹-1 to R¹-92, more preferably R¹-1 to R¹-54.

A preferred embodiment of the compounds of the formula (TA-3) is the compounds of the following formula (TA-3a):

where Ar⁵ and R¹ have the definitions listed above, especially for formulae (I) and/or (TA-1). Preferred embodiments of the Ar⁵ group are the above-listed structures R¹-1 to R¹-92, more preferably R¹-1 to R¹-54.

Preferred lactams which are used as co-host materials together with the compounds of the invention are selected from the compounds of the following formula (LAC-1):

where R¹ has the definition listed above, especially for formula (I).

A preferred embodiment of the compounds of the formula (LAC-1) is the compounds of the following formula (LAC-1a):

where R¹ has the definition given above, especially for formula (I). R¹ here is preferably the same or different at each instance and is H or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted by one or more R² radicals, where R² may have the definition given above, especially for formula (I). Most preferably, the R¹ substituents are selected from the group consisting of H and an aromatic or heteroaromatic ring system which has 6 to 18 aromatic ring atoms, preferably 6 to 13 aromatic ring atoms, and may be substituted in each case by one or more nonaromatic R² radicals, but is preferably unsubstituted. Examples of suitable R¹ substituents are selected from the group consisting of phenyl, ortho-, meta- or para-biphenyl, terphenyl, especially branched terphenyl, quaterphenyl, especially branched quaterphenyl, 1-, 2-, 3- or 4-fluorenyl, 1-, 2-, 3- or 4-spirobifluorenyl, pyridyl, pyrimidinyl, 1-, 2-, 3- or 4-dibenzofuranyl, 1-, 2-, 3- or 4-dibenzothienyl and 1-, 2-, 3- or 4-carbazolyl, each of which may be substituted by one or more R² radicals, but are preferably unsubstituted. Suitable R¹ structures here are the same structures as depicted above for R-1 to R-79, more preferably R¹-1 to R¹-51.

It may also be preferable to use a plurality of different matrix materials as a mixture, especially at least one electron-conducting matrix material and at least one hole-conducting matrix material. Preference is likewise given to the use of a mixture of a charge-transporting matrix material and an electrically inert matrix material having no significant involvement, if any, in the charge transport, as described, for example, in WO 2010/108579.

It is further preferable to use a mixture of two or more triplet emitters together with a matrix. In this case, the triplet emitter having the shorter-wave emission spectrum serves as co-matrix for the triplet emitter having the longer-wave emission spectrum.

More preferably, it is possible to use a compound of the invention comprising structures of formula (I), in a preferred embodiment, as matrix material in an emission layer of an organic electronic device, especially in an organic electroluminescent device, for example in an OLED or OLEC. In this case, the matrix material containing compound comprising structures of formula (I) or the preferred embodiments recited above and hereinafter is present in the electronic device in combination with one or more dopants, preferably phosphorescent dopants.

The proportion of the matrix material in the emitting layer in this case is between 50.0% and 99.9% by volume, preferably between 80.0% and 99.5% by volume, and more preferably between 92.0% and 99.5% by volume for fluorescent emitting layers and between 85.0% and 97.0% by volume for phosphorescent emitting layers.

Correspondingly, the proportion of the dopant is between 0.1% and 50.0% by volume, preferably between 0.5% and 20.0% by volume, and more preferably between 0.5% and 8.0% by volume for fluorescent emitting layers and between 3.0% and 15.0% by volume for phosphorescent emitting layers.

An emitting layer of an organic electroluminescent device may also comprise systems comprising a plurality of matrix materials (mixed matrix systems) and/or a plurality of dopants. In this case too, the dopants are generally those materials having the smaller proportion in the system and the matrix materials are those materials having the greater proportion in the system. In individual cases, however, the proportion of a single matrix material in the system may be less than the proportion of a single dopant.

In a further preferred embodiment of the invention, the compound comprising structures of formula (I) or the preferred embodiments recited above and below are used as a component of mixed matrix systems. The mixed matrix systems preferably comprise two or three different matrix materials, more preferably two different matrix materials. Preferably, in this case, one of the two materials is a material having hole-transporting properties and the other material is a material having electron-transporting properties. The desired electron-transporting and hole-transporting properties of the mixed matrix components may, however, also be combined mainly or entirely in a single mixed matrix component, in which case the further mixed matrix component(s) fulfil(s) other functions. The two different matrix materials may be present in a ratio of 1:50 to 1:1, preferably 1:20 to 1:1, more preferably 1:10 to 1:1 and most preferably 1:4 to 1:1. Preference is given to using mixed matrix systems in phosphorescent organic electroluminescent devices. One source of more detailed information about mixed matrix systems is the application WO 2010/108579.

The present invention further provides an electronic device, preferably an organic electroluminescent device, comprising one or more compounds of the invention and/or at least one oligomer, polymer or dendrimer of the invention in one or more electron-conducting layers, as electron-conducting compound.

Preferred cathodes are metals having a low work function, metal alloys or multilayer structures composed of various metals, for example alkaline earth metals, alkali metals, main group metals or lanthanoids (e.g. Ca, Ba, Mg, Al, In, Mg, Yb, Sm, etc.). Additionally suitable are alloys composed of an alkali metal or alkaline earth metal and silver, for example an alloy composed of magnesium and silver. In the case of multilayer structures, in addition to the metals mentioned, it is also possible to use further metals having a relatively high work function, for example Ag, in which case combinations of the metals such as Mg/Ag, Ca/Ag or Ba/Ag, for example, are generally used. It may also be preferable to introduce a thin interlayer of a material having a high dielectric constant between a metallic cathode and the organic semiconductor. Examples of useful materials for this purpose are alkali metal or alkaline earth metal fluorides, but also the corresponding oxides or carbonates (e.g. LiF, Li₂O, BaF₂, MgO, NaF, CsF, Cs₂CO₃, etc.). Likewise useful for this purpose are organic alkali metal complexes, e.g. Liq (lithium quinolinate). The layer thickness of this layer is preferably between 0.5 and 5 nm.

Preferred anodes are materials having a high work function. Preferably, the anode has a work function of greater than 4.5 eV versus vacuum. Firstly, metals having a high redox potential are suitable for this purpose, for example Ag, Pt or Au. Secondly, metal/metal oxide electrodes (e.g. Al/Ni/NiO_(x), Al/PtO_(x)) may also be preferred. For some applications, at least one of the electrodes has to be transparent or partly transparent in order to enable either the irradiation of the organic material (O-SC) or the emission of light (OLED/PLED, O-laser). Preferred anode materials here are conductive mixed metal oxides. Particular preference is given to indium tin oxide (ITO) or indium zinc oxide (IZO). Preference is further given to conductive doped organic materials, especially conductive doped polymers, for example PEDOT, PANI or derivatives of these polymers. It is further preferable when a p-doped hole transport material is applied to the anode as hole injection layer, in which case suitable p-dopants are metal oxides, for example MoO₃ or WO₃, or (per)fluorinated electron-deficient aromatic systems. Further suitable p-dopants are HAT-CN (hexacyanohexaazatriphenylene) or the compound NPD9 from Novaled. Such a layer simplifies hole injection into materials having a low HOMO, i.e. a large HOMO in terms of magnitude.

In the further layers, it is generally possible to use any materials as used according to the prior art for the layers, and the person skilled in the art is able, without exercising inventive skill, to combine any of these materials with the materials of the invention in an electronic device.

The device is correspondingly (according to the application) structured, contact-connected and finally hermetically sealed, since the lifetime of such devices is severely shortened in the presence of water and/or air.

Additionally preferred is an electronic device, especially an organic electroluminescent device, which is characterized in that one or more layers are coated by a sublimation process. In this case, the materials are applied by vapour deposition in vacuum sublimation systems at an initial pressure of typically less than 10⁻⁵ mbar, preferably less than 10⁻⁶ mbar. It is also possible that the initial pressure is even lower or even higher, for example less than 10⁻⁷ mbar.

Preference is likewise given to an electronic device, especially an organic electroluminescent device, which is characterized in that one or more layers are coated by the OVPD (organic vapour phase deposition) method or with the aid of a carrier gas sublimation. In this case, the materials are applied at a pressure between 10⁻⁵ mbar and 1 bar. A special case of this method is the OVJP (organic vapour jet printing) method, in which the materials are applied directly by a nozzle and thus structured (for example M. S. Arnold et at, Appl. Phys. Lett. 2008, 92, 053301).

Preference is additionally given to an electronic device, especially an organic electroluminescent device, which is characterized in that one or more layers are produced from solution, for example by spin-coating, or by any printing method, for example screen printing, flexographic printing, offset printing or nozzle printing, but more preferably LITI (light-induced thermal imaging, thermal transfer printing) or inkjet printing. For this purpose, soluble compounds are needed, which are obtained, for example, through suitable substitution.

The electronic device, especially the organic electroluminescent device, can also be produced as a hybrid system by applying one or more layers from solution and applying one or more other layers by vapour deposition. For example, it is possible to apply an emitting layer comprising a compound of the invention comprising structures of formula (I) and a matrix material from solution, and to apply a hole blocker layer and/or an electron transport layer thereto by vapour deposition under reduced pressure.

These methods are known in general terms to those skilled in the art and can be applied without difficulty to electronic devices, especially organic electroluminescent devices containing compounds of the invention comprising structures of formula (I) or the above-detailed preferred embodiments.

The electronic devices of the invention, especially organic electroluminescent devices, are notable for one or more of the following surprising advantages over the prior art:

-   1. Electronic devices, especially organic electroluminescent     devices, comprising compounds, oligomers, polymers or dendrimers     having structures of formula (I) or the preferred embodiments     recited above and hereinafter, especially as electron-conducting     materials and/or hole conductor materials or as matrix materials,     have a very good lifetime. -   2. Electronic devices, especially organic electroluminescent     devices, comprising compounds, oligomers, polymers or dendrimers     having structures of formula (I) or the preferred embodiments     recited above and hereinafter, especially as electron transport     materials, hole conductor materials and/or as host materials, have     excellent efficiency. More particularly, efficiency is much higher     compared to analogous compounds containing no structural unit of     formula (I). In this context, the compounds, oligomers, polymers or     dendrimers of the invention having structures of formula (I) or the     preferred embodiments recited above and hereinafter bring about a     low operating voltage when used in electronic devices. In this     context, these compounds especially bring about low roll-off, i.e. a     small drop in power efficiency of the device at high luminances. -   3. Electronic devices, especially organic electroluminescent     devices, comprising compounds, oligomers, polymers or dendrimers     having structures of formula (I) or the preferred embodiments     recited above and hereinafter, as electron transport materials, hole     conductor materials and/or as host materials, have excellent colour     purity. -   4. The compounds, oligomers, polymers or dendrimers of the invention     having structures of formula (I) or the preferred embodiments     recited above and hereinafter exhibit very high thermal and     photochemical stability and lead to compounds having a very long     lifetime. -   5. With compounds, oligomers, polymers or dendrimers having     structures of formula (I) or the preferred embodiments recited above     and hereinafter, it is possible to avoid the formation of optical     loss channels in electronic devices, especially organic     electroluminescent devices. As a result, these devices feature a     high PL efficiency and hence high EL efficiency of emitters, and     excellent energy transmission of the matrices to dopants. -   6. Compounds, oligomers, polymers or dendrimers having structures of     formula (I) or the preferred embodiments recited above and     hereinafter have excellent glass film formation. -   7. Compounds, oligomers, polymers or dendrimers having structures of     formula (I) or the preferred embodiments recited above and     hereinafter form very good films from solutions.

These abovementioned advantages are not accompanied by a deterioration in the further electronic properties.

The compounds and mixtures of the invention are suitable for use in an electronic device. An electronic device is understood to mean a device containing at least one layer containing at least one organic compound. The component may also comprise inorganic materials or else layers formed entirely from inorganic materials.

The present invention therefore further provides for the use of the compounds or mixtures of the invention in an electronic device, especially in an organic electroluminescent device.

The present invention still further provides for the use of a compound of the invention and/or of an oligomer, polymer or dendrimer of the invention in an electronic device as host material, hole conductor material, electron injection material and/or electron transport material, preferably as host material and/or electron transport material.

The present invention still further provides an electronic device comprising at least one of the above-detailed compounds or mixtures of the invention. In this case, the preferences detailed above for the compound also apply to the electronic devices. More preferably, the electronic device is selected from the group consisting of organic electroluminescent devices (OLEDs, PLEDs), organic integrated circuits (O-ICs), organic field-effect transistors (O-FETs), organic thin-film transistors (O-TFTs), organic light-emitting transistors (O-LETs), organic solar cells (O-SCs), organic optical detectors, organic photoreceptors, organic field-quench devices (O-FQDs), organic electrical sensors, light-emitting electrochemical cells (LECs), organic laser diodes (O-lasers) and organic plasmon emitting devices, preferably organic electroluminescent devices (OLEDs, PLEDs), especially phosphorescent OLEDs.

In a further embodiment of the invention, the organic electroluminescent device of the invention does not contain any separate hole injection layer and/or hole transport layer and/or hole blocker layer and/or electron transport layer, meaning that the emitting layer directly adjoins the hole injection layer or the anode, and/or the emitting layer directly adjoins the electron transport layer or the electron injection layer or the cathode, as described, for example, in WO 2005/053051. It is additionally possible to use a metal complex identical or similar to the metal complex in the emitting layer as hole transport or hole injection material directly adjoining the emitting layer, as described, for example, in WO 2009/030981.

In the further layers of the organic electroluminescent device of the invention, it is possible to use any materials as typically used according to the prior art. The person skilled in the art is therefore able, without exercising inventive skill, to use any materials known for organic electroluminescent devices in combination with the inventive compounds of formula (I) or according to the preferred embodiments.

The compounds of the invention generally have very good properties on use in organic electroluminescent devices. Especially in the case of use of the compounds of the invention in organic electroluminescent devices, the lifetime is significantly better compared to similar compounds according to the prior art. At the same time, the further properties of the organic electroluminescent device, especially the efficiency and voltage, are likewise better or at least comparable.

It should be pointed out that variations of the embodiments described in the present invention are covered by the scope of this invention. Any feature disclosed in the present invention may, unless this is explicitly ruled out, be exchanged for alternative features which serve the same purpose or an equivalent or similar purpose. Thus, any feature disclosed in the present invention, unless stated otherwise, should be considered as an example of a generic series or as an equivalent or similar feature.

All features of the present invention may be combined with one another in any manner, unless particular features and/or steps are mutually exclusive. This is especially true of preferred features of the present invention. Equally, features of non-essential combinations may be used separately (and not in combination).

It should also be pointed out that many of the features, and especially those of the preferred embodiments of the present invention, should themselves be regarded as inventive and not merely as some of the embodiments of the present invention. For these features, independent protection may be sought in addition to or as an alternative to any currently claimed invention.

The technical teaching disclosed with the present invention may be abstracted and combined with other examples.

The invention is illustrated in detail by the examples which follow, without any intention of restricting it thereby. The person skilled in the art will be able to use the details given, without exercising inventive skill, to produce further electronic devices of the invention and hence to execute the invention over the entire scope claimed.

EXAMPLES

The syntheses which follow, unless stated otherwise, are conducted under a protective gas atmosphere in dried solvents. The reactants can be sourced from ALDRICH. The numbers for the reactants known from the literature, some of which are stated in square brackets, are the corresponding CAS numbers.

Synthesis Examples a) Benzo[kl]xanthen-9-yl-(2-chlorophenyl)amine

40 g (137 mmol) of 9-bromobenzo[kl]xanthene, 17.9 g (140 mmol) of 2-chloroaniline, 68.2 g (710 mmol) of sodium tert-butoxide, 613 mg (3 mmol) of palladium(II) acetate and 3.03 g (5 mmol) of dppf are dissolved in 1.3 I of toluene and stirred under reflux for 5 h. The reaction mixture is cooled down to room temperature, extended with toluene and filtered through Celite. The filtrate is concentrated under reduced pressure and the residue is crystallized from toluene/heptane. The product is isolated as a colourless solid. Yield: 39 g (109 mmol); 83% of theory.

The following compounds can be prepared in an analogous manner:

Reactant 1 Reactant 2 Product Yield 1a

81% 2a

75% 3a

76% 4a

72% 5a

79% 6a

71% 7a

73% 8a

77% 9a

70% 10a

70% 11a

71% 12a

76% 13a

70% 14a

69% 15a

71% 16a

67% 17a

71%

b) Cyclization

35 g (102 mmol) of benzo[kl]xanthen-9-yl-(2-chlorophenyl)amine, 56 g (409 mmol) of potassium carbonate, 4.5 g (12 mmol) of tricyclohexylphosphine tetrafluoroborate and 1.38 g (6 mmol) of palladium(II) acetate are suspended in 500 ml of dimethylacetamide and stirred under reflux for 6 h. After cooling, the reaction mixture is admixed with 300 ml of water and 400 ml of ethyl acetate. The mixture is stirred for a further 30 min, the organic phase is separated off and filtered through a short Celite bed, and then the solvent is removed under reduced pressure. The crude product is subjected to hot extraction with toluene and recrystallized from toluene. Yield: 28 g (229 mmol) of the A+B mixture; 90% of theory; purity: 98.0% by HPLC. After recrystallization from ethyl acetate/toluene (1:2), 62% A and 23% B are obtained.

The following compounds can be prepared in an analogous manner:

Reactant 1 Product 1b

2b

3b

4b

5b

6b

7b

8b

9b

10b

11b

12b

13b

14b

15b

16b

Product Yield 1b

60%/19% 2b 72% 3b

54%/22% 4b

59%/18% 5b 67% 6b

56%/20% 7b

53%/19% 8b

50%/21% 9b

59%/11% 10b

50%/20% 11b 77% 12b

61%/15% 13b

59%/16% 14b 72% 15b

55%/22% 16b

41%/24%

c) Buchwald

4.3 g of NaH (107 mmol), 60% in mineral oil, are dissolved in 300 ml of dimethylformamide under a protective atmosphere. 32 g (107 mmol) of carbazole derivative (A) are dissolved in 250 ml of DMF and added dropwise to the reaction mixture. After 1 h at room temperature, a solution of 2-chloro-4,6-diphenyl-[1,3,5]-triazine (34.5 g, 0.122 mol) in 200 ml of THF is added dropwise. The reaction mixture is stirred at room temperature for 12 h and then poured onto ice. After warming to room temperature, the solids that precipitate out are filtered and washed with ethanol and heptane. The residue is subjected to hot extraction with toluene, recrystallized from toluene/n-heptane and finally sublimed under high vacuum. The purity is 99.9%. The yield is 38 g (70 mmol); 66% of theory.

The following compounds can be prepared in an analogous manner:

Reactant 1 Reactant 2 1c

2c

3c

4c

5c

6c

7c

8c

9c

10c

11c

12c

13c

14c

15c

16c

17c

18c

19c

20c

21c

22c

23c

24c

25c

26c

27v

28c

29c

30c

31c

32c

33c

34c

Product Yield 1c

66% 2c

62% 3c

64% 4c

57% 5c

61% 6c

63% 7c

60% 8c

68% 9c

65% 10c

69% 11c

67% 12c

64% 13c

63% 14c

68% 15c

65% 16c

62% 17c

65% 18c

71% 19c

69% 20c

73% 21c

70% 22c

63% 23c

60% 24c

71% 25c

7% 26c

69% 27v

63% 28c

64% 29c

70% 30c

76% 31c

65% 32c

69% 33c

72% 34c

74%

Production of the OLEDs

In examples I1 to I19 which follow, the data of various OLEDs are presented.

Pretreatment for Examples I1-I19:

Glass plaques coated with structured ITO (indium tin oxide) of thickness 50 nm are treated prior to coating with an oxygen plasma, followed by an argon plasma. These plasma-treated glass plaques form the substrates to which the OLEDs are applied.

The OLEDs basically have the following layer structure: substrate/hole injection layer (HIL)/hole transport layer (HTL)/electron blocker layer (EBL)/emission layer (EML)/optional hole blocker layer (HBL)/electron transport layer (ETL)/optional electron injection layer (EIL) and finally a cathode. The cathode is formed by an aluminium layer of thickness 100 nm. The exact structure of the OLEDs can be found in Table 1. The materials required for production of the OLEDs are shown in Table 2.

All materials are applied by thermal vapour deposition in a vacuum chamber. In this case, the emission layer always consists of at least one matrix material (host material) and an emitting dopant (emitter) which is added to the matrix material(s) in a particular proportion by volume by co-evaporation. Details given in such a form as IC5:1C3:TEG2 (55%:35%:10%) mean here that the material 105 is present in the layer in a proportion by volume of 55%, IC3 in a proportion of 35% and TEG2 in a proportion of 10%. Analogously, the electron transport layer may also consist of a mixture of two materials.

The OLEDs are characterized in a standard manner. For this purpose, the electroluminescence spectra, the current efficiency (measured in cd/A), the power efficiency (measured in lm/W) and the external quantum efficiency (EQE, measured in percent) as a function of luminance, calculated from current-voltage-luminance characteristics (IUL characteristics) assuming Lambertian emission characteristics, and also the lifetime are determined. The electroluminescence spectra are determined at a luminance of 1000 cd/m², and the CIE 1931 x and y colour coordinates are calculated therefrom.

Use of Mixtures of the Invention in the Emission Layer of Phosphorescent OLEDs

The materials of the invention can be used in the emission layer in phosphorescent red OLEDs. The inventive material EG1 is used in Example I1 as matrix material in combination with the phosphorescent emitter TEG5. At a luminance of 1000 cd/m², the OLED has colour coordinates of CIEx=0.67 and CIEy=0.33. In examples I2 to I13 too, the OLED emits light with the colour coordinates CIEx=0.67 and CIEy=0.33. This shows that the inventive compounds EG1-EG13 are suitable for use as matrix material in OLEDs.

Use of Mixtures of the Invention in the Electron Transport Layer of Phosphorescent OLEDs

The materials of the invention can also be used in the electron transport layer in OLEDs. In Examples 114 to 119, the inventive materials EG14 to EG19 are used in the electron transport layer. In examples I14 to I19, the OLED emits light with the colour coordinates CIEx=0.67 and CIEy=0.33. This shows that the inventive compounds EG14 to EG19 are suitable for use as electron transport material in OLEDs.

TABLE 1 Structure of the OLEDs HIL HTL EBL EML HBL ETL EIL Ex. thickness thickness thickness thickness thickness thickness thickness I1 HATCN SpMA1 SpMA3 EG1:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I2 HATCN SpMA1 SpMA3 EG2:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I3 HATCN SpMA1 SpMA3 EG3:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I4 HATCN SpMA1 SpMA3 EG4:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I5 HATCN SpMA1 SpMA3 EG5:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I6 HATCN SpMA1 SpMA3 EG6:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I7 HATCN SpMA1 SpMA3 EG7:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I8 HATCN SpMA1 SpMA3 EG8:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I9 HATCN SpMA1 SpMA3 EG9:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I10 HATCN SpMA1 SpMA3 EG10:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I11 HATCN SpMA1 SpMA3 EG11:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I12 HATCN SpMA1 SpMA3 EG12:TER5 ST2:LiQ 5 nm 125 nm 10 nm (95%:5%) (50%:50%) 40 nm 35 nm I13 HATCN SpMA1 SpMA3 EG1:TER5 ST2 ST2:EG13 LiQ 5 nm 125 nm 10 nm (95%:5%) 5 nm (50%:50%) 3 nm 40 nm 30 nm I14 HATCN SpMA1 SpMA3 EG1:TER5 ST2 ST2:EG14 LiQ 5 nm 125 nm 10 nm (95%:5%) 5 nm (50%:50%) 3 nm 40 nm 30 nm I15 HATCN SpMA1 SpMA3 EG1:TER5 ST2 ST2:EG15 LiQ 5 nm 125 nm 10 nm (95%:5%) 5 nm (50%:50%) 3 nm 40 nm 30 nm I16 HATCN SpMA1 SpMA3 EG1:TER5 ST2 ST2:EG16 LiQ 5 nm 125 nm 10 nm (95%:5%) 5 nm (50%:50%) 3 nm 40 nm 30 nm I17 HATCN SpMA1 SpMA3 EG1:TER5 ST2 ST2:EG17 LiQ 5 nm 125 nm 10 nm (95%:5%) 5 nm (50%:50%) 3 nm 40 nm 30 nm I18 HATCN SpMA1 SpMA3 EG1:TER5 ST2 ST2:EG18 LiQ 5 nm 125 nm 10 nm (95%:5%) 5 nm (50%:50%) 3 nm 40 nm 30 nm I19 HATCN SpMA1 SpMA3 EG1:TER5 ST2 ST2:EG19 LiQ 5 nm 125 nm 10 nm (95%:5%) 5 nm (50%:50%) 3 nm 40 nm 30 nm

TABLE 2 Structural formulae of the materials for the OLEDs

HATCN

SpMA1

SpMA3

ST2

TER5

LiQ

EG1

EG2

EG3

EG4

EG5

EG6

EG7

EG8

EG9

EG10

EG11

EG12

EG13

EG14

EG15

EG16

EG17

EG18

EG19 

1.-15. (canceled)
 16. A compound comprising at least one structure of the formula (I)

where the symbols used are as follows: X is the same or different at each instance and is N or CR¹, or C if the indolo group is bonded to X; W¹ is O, S, C(R¹)₂, P(═O)Ar or Si(R¹)₂; R¹ is the same or different at each instance and is H, D, F, Cl, Br, I, CN, NO₂, N(Ar¹)₂, N(R²)₂, C(═O)Ar¹, C(═O)R², P(═O)(Ar¹)₂, P(Ar¹)₂, B(Ar¹)₂, B(OR²)₂, Si(Ar¹)₃, Si(R²)₃, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 carbon atoms or an alkenyl group having 2 to 40 carbon atoms, each of which may be substituted by one or more R² radicals, where one or more nonadjacent CH₂ groups may be replaced by —R²C═CR²—, —C≡C—, Si(R²)₂, Ge(R²)₂, Sn(R²)₂, C═O, C═S, C═Se, C═NR², —C(═O)O—, —C(═O)NR²—, NR², P(═O)(R²), —O—, —S—, SO or SO₂ and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R² radicals, or an aryloxy or heteroaryloxy group which has 5 to 40 aromatic ring atoms and may be substituted by one or more R² radicals, or an aralkyl or heteroaralkyl group which has 5 to 40 aromatic ring atoms and may be substituted by one or more R² radicals, or a combination of these systems; at the same time, two or more R¹ radicals together may form a mono- or polycyclic, aliphatic, heteroaliphatic, aromatic or heteroaromatic ring system; Ar is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 60 aromatic ring atoms and may be substituted by one or more R¹ radicals; Ar¹ is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 30 aromatic ring atoms and may be substituted by one or more R² radicals; at the same time, two Ar¹ radicals bonded to the same silicon atom, nitrogen atom, phosphorus atom or boron atom may also be joined together via a bridge by a single bond or a bridge selected from the group consisting of B(R²), C(R²)₂, Si(R²)₂, C═O, C═NR², C═C(R²)₂O, S, S═O, SO₂, N(R), P(R²) and P(═O)R²; R² is the same or different at each instance and is H, D, F, Cl, Br, I, CN, B(OR³)₂, NO₂, C(═O)R³, CR³═C(R³)₂, C(═O)OR³, C(═O)N(R³)₂, Si(R³)₃, P(R³)₂, B(R³)₂, N(R³)₂, NO₂, P(═O)(R³)₂, OSO₂R³, OR³, S(═O)R³, S(═O)₂R³, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of which may be substituted by one or more R³ radicals, where one or more nonadjacent CH₂ groups may be replaced by —R³C═CR³—, —C≡C—, Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═NR³, —C(═O)O—, —C(═O)NR³—, NR³, P(═O)(R³), —O—, —S—, SO or SO₂ and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R³ radicals, or an aryloxy or heteroaryloxy group which has 5 to 40 aromatic ring atoms and may be substituted by one or more R³ radicals, or a combination of these systems; at the same time, two or more R² substituents together may also form a mono- or polycyclic, aliphatic, heteroaliphatic, aromatic or heteroaromatic ring system; R³ is the same or different at each instance and is selected from the group consisting of H, D, F, CN, an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, or an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms in which one or more hydrogen atoms may be replaced by D, F, Cl, Br, I or CN and which may be substituted by one or more alkyl groups each having 1 to 4 carbon atoms; at the same time, two or more R³ substituents together may also form a mono- or polycyclic, aliphatic, heteroaliphatic, aromatic or heteroaromatic ring system.
 17. The compound according to claim 16, comprising at least one structure of the formula (IIa), (IIb), (IIc), (IId), (IIe) or (IIf)

where symbols Ar, W¹ and X used have the definition given in claim
 16. 18. The compound according to claim 16, comprising at least one structure of the formula (IIIa), (IIIb), (IIIc), (IIId), (IIIe) or (IIIf)

where symbols R¹, Ar, W¹ and X have the definition given in claim 16 and m is 0, 1, 2, 3 or
 4. 19. The compound according to claim 16, comprising at least one structure of the formula (IVa), (IVb), (IVc), (IVd), (IVe) or (IVf)

where symbols R¹, Ar, W¹ and X have the definition given in claim 16 and o is 0, 1 or
 2. 20. The compound according to claim 16, comprising at least one structure of the formula (Va), (Vb), (Vc), (Vd), (Ve) or (Vf)

where symbols R¹, Ar, W¹ and X used have the definition given in claim 16 and l is 0, 1, 2, 3, 4, 5 or
 6. 21. The compound according to claim 16, comprising at least one structure of the formula (VIa), (VIb), (VIc), (VId), (VIe) or (VIf)

where symbols R¹, Ar, W¹ and X have the definition given in claim 16, l is 0, 1, 2, 3, 4, 5 or 6, m is 0, 1, 2, 3 or 4 and o is 0, 1 or
 2. 22. The compound according to claim 16, wherein the Ar group comprises or constitutes a hole transport group.
 23. The compound according to claim 16, wherein the Ar group comprises or constitutes an electron transport group.
 24. The compound according to claim 23, wherein the Ar group is a group that can be represented by the formula (QL) Q-L¹-   Formula (QL) in which L¹ represents a bond or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted by one or more R¹ radicals, and Q is an electron transport group, where R¹ is the same or different at each instance and is H, D, F, Cl, Br, I, CN, NO₂, N(Ar¹)₂, N(R²)₂, C(═O)Ar¹, C(═O)R², P(═O)(Ar¹)₂, P(Ar¹)₂, B(Ar¹)₂, B(OR²)₂, Si(Ar¹)₃, Si(R²)₃, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 carbon atoms or an alkenyl group having 2 to 40 carbon atoms, each of which may be substituted by one or more R² radicals, where one or more nonadjacent CH₂ groups may be replaced by —R²C═CR²—, —C≡C—, Si(R²)₂, Ge(R²)₂, Sn(R²)₂, C═O, C═S, C═Se, C═NR², —C(═O)O—, —C(═O)NR²—, NR², P(═O)(R²), —O—, —S—, SO or SO₂ and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R² radicals, or an aryloxy or heteroaryloxy group which has 5 to 40 aromatic ring atoms and may be substituted by one or more R² radicals, or an aralkyl or heteroaralkyl group which has 5 to 40 aromatic ring atoms and may be substituted by one or more R² radicals, or a combination of these systems; at the same time, two or more R¹ radicals together may form a mono- or polycyclic, aliphatic, heteroaliphatic, aromatic or heteroaromatic ring system; Ar¹ is the same or different at each instance and is an aromatic or heteroaromatic ring system which has 5 to 30 aromatic ring atoms and may be substituted by one or more R² radicals; at the same time, two Ar¹ radicals bonded to the same silicon atom, nitrogen atom, phosphorus atom or boron atom may also be joined together via a bridge by a single bond or a bridge selected from the group consisting of B(R²), C(R²)₂, Si(R²)₂, C═O, C═C(R²)₂, O, S, S═O, SO₂, N(R²), P(R²) and P(═O)R²; R² is the same or different at each instance and is H, D, F, Cl, Br, I, CN, B(OR³)₂, NO₂, C(═O)R³, CR³═C(R³)₂, C(═O)OR³, C(═O)N(R³)₂, Si(R³)₃, P(R³)₂, B(R³)₂, N(R³)₂, NO₂, P(═O)(R³)₂, OSO₂R³, OR³, S(═O)R³, S(═O)₂R³, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a branched or cyclic alkyl, alkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of which may be substituted by one or more R³ radicals, where one or more nonadjacent CH₂ groups may be replaced by —R³C═CR³—, —C≡C—, Si(R³)₂, Ge(R³)₂, Sn(R³)₂, C═O, C═S, C═NR³, —C(═O)O—, —C(═O)NR³—, NR³, P(═O)(R³), —O—, —S—, SO or SO₂ and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, or an aromatic or heteroaromatic ring system which has 5 to 40 aromatic ring atoms and may be substituted in each case by one or more R³ radicals, or an aryloxy or heteroaryloxy group which has 5 to 40 aromatic ring atoms and may be substituted by one or more R³ radicals, or a combination of these systems; at the same time, two or more R² substituents together may also form a mono- or polycyclic, aliphatic, heteroaliphatic, aromatic or heteroaromatic ring system; and R³ is the same or different at each instance and is selected from the group consisting of H, D, F, CN, an aliphatic hydrocarbyl radical having 1 to 20 carbon atoms, or an aromatic or heteroaromatic ring system having 5 to 30 aromatic ring atoms in which one or more hydrogen atoms may be replaced by D, F, Cl, Br, I or CN and which may be substituted by one or more alkyl groups each having 1 to 4 carbon atoms; at the same time, two or more R³ substituents together may also form a mono- or polycyclic, aliphatic, heteroaliphatic, aromatic or heteroaromatic ring system.
 25. An oligomer, polymer or dendrimer containing one or more compounds according to claim 16, wherein, rather than a hydrogen atom or a substituent, there are one or more bonds of the compounds to the polymer, oligomer or dendrimer.
 26. A composition comprising at least one compound according to claim 16 and at least one further compound selected from the group consisting of fluorescent emitters, phosphorescent emitters, emitters that exhibit TADF, host materials, electron transport materials, electron injection materials, hole conductor materials, hole injection materials, electron blocker materials and hole blocker materials.
 27. A composition comprising the oligomer, polymer or dendrimer according to claim 25 and at least one further compound selected from the group consisting of fluorescent emitters, phosphorescent emitters, emitters that exhibit TADF, host materials, electron transport materials, electron injection materials, hole conductor materials, hole injection materials, electron blocker materials and hole blocker materials.
 28. A formulation comprising at least one compound according to claim 16 and at least one solvent.
 29. A formulation comprising the composition according to claim 26 and at least one solvent.
 30. An electronic device as host material, hole conductor material or electron transport material which comprises the compound according to claim
 16. 31. A process for preparing the compound according to claim 16 which comprises a coupling reaction, joining a compound comprising at least one nitrogen-containing heterocyclic group to a compound comprising at least one aromatic or heteroaromatic group.
 32. An electronic device comprising at least one compound according to claim
 16. 33. The electronic device as claimed in claim 32, wherein the electronic device is selected from the group consisting of organic electroluminescent devices, organic integrated circuits, organic field-effect transistors, organic thin-film transistors, organic light-emitting transistors, organic solar cells, organic optical detectors, organic photoreceptors, organic field-quench devices, light-emitting electrochemical cells and organic laser diodes. 